9 CARDIOVASCULAR DISEASE, HYPERTENSION AND DIABETES
Andy MacGregor and Jennifer Mindell
- Rates of cardiovascular disease ( CVD) were similar in men (15.2%) and women (13.7%) aged 16 and over in 2009.
- CVD or diabetes prevalence was significantly higher for men than for women (18.9% and 16.5%, respectively) and increased markedly with age for both sexes to 55.5% of men and 41.8% of women aged 75 and over.
- The prevalence of ischaemic heart disease ( IHD) was 7.3% for men and 5.2% for women, while 9.4% of men and 6.7% of women had IHD or stroke. Prevalence of these conditions also increased with age.
- There was a significant increase in the proportion of men aged 16-64 with any CVD or diabetes between 1995 and 2009 (from 9.4% to 12.6%). This was largely caused by an increase in the prevalence of diabetes. There was no clear trend in the figures for women over this period.
- In 2008/2009, 5.0% of adults aged 16 and over had doctor-diagnosed diabetes (5.7% of men and 4.3% of women).
- Prevalence of doctor-diagnosed diabetes among adults aged 16-64 has increased significantly over time. For men, it increased from 1.5% in 1995 to 4.0% in 2008/2009. The equivalent figures for women were 1.5% and 2.9%, respectively.
- The prevalence of possible undiagnosed diabetes (as measured by glycated haemoglobin in blood samples) was 2.5% in 2008/2009. This had doubled since 2003 when the prevalence was 1.1%.
- Prevalence of possible undiagnosed diabetes was greatest among those aged 65-74.
- Around a third of adults (34.6% of men and 30.2% of women) had high blood pressure (hypertension) in 2008/2009.
- Hypertension increased significantly with age for both men and women, and with the exception of the 75 and over age group, prevalence was higher for men than for women.
- One in five (20.1%) men and one in seven (14.3%) women aged 16 and over had untreated hypertension. Prevalence increased with age and was highest for men and women aged 55 and over.
- People with CVD were more likely than those without it to have low activity levels, be overweight or obese, be an ex-smoker, have a family history of CVD, have hypertension and have diabetes. They were also more likely than those without CVD to live in semi-routine or routine households, be in the lowest income quintile households and live in the most deprived areas. Those without CVD were more likely than those with it to be current smokers, to exceed the recommendations on weekly alcohol consumption and to have raised total cholesterol. Similar patterns were found when people with and without IHD were compared.
- For both men and women the odds of having any CVD condition increased with age and were higher in those who were ex-regular smokers and those with lower activity levels. Those with doctor-diagnosed diabetes and raised total cholesterol levels also had increased odds of having any CVD condition. Women exceeding the recommendations for weekly alcohol consumption had lower odds than those who did not, while men living in the most deprived areas of Scotland had higher odds than those living in the least deprived areas of having a CVD condition.
The main focus of this chapter is cardiovascular disease ( CVD). It also presents findings about diabetes and hypertension. Future Scottish Health Survey reports will include more detailed explorations of both these topics; their inclusion in this chapter is a reflection of their status as major health burdens and risk factors for CVD.
CVD is one of the leading contributors to the global disease burden. Its main components are ischaemic heart disease ( IHD) and stroke. In this report, the term IHD is used interchangeably with CHD (coronary heart disease). IHD is the second most common cause of death in Scotland after cancer; in 2009, 15% of deaths were attributed to it and a further 9% were caused by stroke. 1 Prevalence of CVD is higher in lower social classes and deprived areas. 2 A number of the Scottish Government's National Performance Framework national indicators 3 have a specific focus on CVD and inequalities. Of most direct relevance here, and outlined in the 2009 Better Heart Disease and Stroke Care Action Plan, 4 is the aspiration to:
Reduce mortality from coronary heart disease among the under 75s in deprived areas
In 2007 the Scottish Government published Better Health, Better Care5, outlining its action plan for improving health and health care in Scotland. This set out how NHS Scotland's HEAT6 performance management system (based around a series of targets against which the performance of its individual Boards are measured) would feed into the Government's overarching objectives. The below HEAT targets also reflect this approach 7:
Achieve agreed number of inequalities targeted cardiovascular Health Checks during 2009/10
Achieve an agreed number of inequalities targeted cardiovascular Health Checks during 2010/11
The introduction to the CVD and diabetes chapter in the 2008 Report outlined the recent policy context for this topic, including a number of strategies and initiatives that have been introduced by the Scottish Government and NHS Scotland to help reduce the prevalence of these conditions. This information is not repeated here, however some recent developments relating to CVD and diabetes follow, as does an overview of the new topic covered in this chapter, hypertension.
Diabetes is a major risk factor for cardiovascular disease and people with a diagnosis of both conditions have significantly worse outcomes in terms of mortality and morbidity than those with a CVD diagnosis alone .8 Diabetes is an endocrinal condition characterised by raised blood glucose levels as a result of impaired insulin function. The condition takes two forms. Type 1 diabetes is caused by an unpreventable autoimmune destruction of the pancreatic cells that produce insulin and its onset is generally, but not always, early on in life. Type 2 diabetes is the more common form of the condition and is estimated to account for around 87% of all cases in Scotland. 8 It occurs when the body becomes unable to respond to insulin, or to produce it, or both. Type 2 diabetes is commonly associated with being overweight or obese. While its prevalence is more common in older age groups, its onset in childhood and early adulthood is increasing. Type 2 diabetes can be prevented, or at least delayed, in many instances.
The 2001 diabetes guidelines ( SIGN no 55), although in force at the time that the data in this report were collected, were superseded by guidelines (no 116) published in March 2010. 9 This covers screening, provision of lifestyle advice and evidence-based interventions (support for weight management, smoking cessation, increased physical activity, healthy eating, moderate alcohol intake), psychological support, regular screening for and management of complications (kidney disease, retinopathy, and diabetic foot disease), and cardiovascular disease prevention. A revised Diabetes Action Plan is due for publication later in 2010.
Blood pressure is the force of the blood pushing against the walls of the arteries. Each time the heart beats, blood is pumped through the arteries to all parts of the body. Blood pressure rises and falls throughout each heartbeat cycle. Systolic blood pressure ( SBP) is the highest pressure in each cycle, and is when the heart contracts and blood is pushed through the arteries. Diastolic blood pressure ( DBP) is when the heart relaxes between beats and refills. Blood pressure is characteristically expressed as two numbers e.g. '140/90' where the 140 is the systolic and the 90 is the diastolic pressure. 10 As well as genetic influences, blood pressure increases in response to dietary salt, alcohol, and obesity and is reduced by physical activity. 10 Damage to the circulatory system results from raised blood pressure - hypertension - which has a number of serious consequences for health. Hypertension is one of the most important risk factors for both ischaemic stroke (where a blood clot interrupts the blood supply to the brain) and for the less common but more serious haemorrhagic stroke (where bleeding occurs in the brain). Hypertension accounts for at least one-third of strokes. 11 In general, one-third of people who develop a stroke will die, one-third recover fully, and one-third remain disabled. Raised blood pressure also contributes to the risk of heart disease. One of the main modifiable determinants of blood pressure level is salt. 12 Reducing population salt intake by 3g daily would reduce SBP by 3.6-5.6mmHg in hypertensives and 0.8-1.8mmHg in normotensives and would result in a 13% reduction in strokes and 10% fall in heart attacks across the UK. 13 The current target is to reduce daily salt intake to less than 6g daily 14 through public education campaigns to discourage individuals from adding salt to their food, 15 and reducing the salt content of manufactured foods. 16
Monitoring diabetes and hypertension are the two most common reasons for patients visiting a practice nurse, accounting for around 80 and 120 contacts respectively per 1,000 registered patients in Scotland. 17
This chapter draws on a wider range of data than the equivalent chapter in the 2008 Report as it takes advantage of the combined 2008/2009 nurse sample data which include direct measures of blood pressure and blood analytes. To make room for these extra analyses the detailed socio-demographic analyses presented last year are not repeated. This chapter reports the prevalence of self-reported CVD conditions and diabetes, rates of potentially undiagnosed diabetes, and hypertension (measured during the nurse visit). Trends in specific conditions and measures in 1995, 1998, 2003, 2008 and 2009, are described and the relationship between various risks factors and CVD is also investigated.
9.2 METHODS AND DEFINITIONS
Participants were asked whether they suffered from any of the following conditions: angina, heart attack, stroke, heart murmur, irregular heart rhythm, 'other heart trouble', and (if they responded affirmatively) whether they had ever been told they had the condition by a doctor. For the purpose of this report, participants were classified as having a particular condition only if they reported that the diagnosis was confirmed by a doctor. Those participants who reported having a particular condition were also asked if they had it in the last 12 months.
Participants were asked whether they suffered from diabetes and, if so, whether they had ever been told they had the condition by a doctor. Only those who reported that the diagnosis was confirmed by a doctor were classified as having diabetes. Women whose diabetes occurred during pregnancy with no subsequent diagnosis after this were excluded from the classification. No distinction was made between type 1 and type 2 diabetes in the interview. In some previous reports rates for each type were estimated by examining the age of onset of the condition and whether a participant was on insulin therapy at the time of interview. 18 However, with increasing rates of type 2 diabetes in younger age groups, and increasing use of insulin to treat it, this classification method is no longer considered appropriate. Rates of potentially undiagnosed diabetes were estimated from non-fasting blood samples of glycated haemoglobin. This is described below.
There have been significant changes to both the definition and measurement of blood pressure since the survey began in 1995. These were discussed in detail in the 2003 survey report and are not repeated here. 19
The 2008 and 2009 surveys used the same measurement equipment (the Omron HEM 907) as used in 2003. The protocol for the measurement of blood pressure in adults remained the same as in all previous years; blood pressure was measured in participants aged 16 and over who took part in the nurse visit. Three blood pressure readings were taken at one minute intervals, on the right arm, with the informant in a seated position, after a five minute rest. Blood pressure of pregnant women was not measured. The detailed protocol for blood pressure measurement is contained in Volume 2 of this report.
The blood pressure levels reported in this chapter are derived from the means of the second and third measurements obtained (from those participants in whom three readings were successfully obtained).
A non-fasting blood sample was obtained from 387 men and 498 women in 2008 and 415 men and 488 women in 2009. Pregnant women, anyone with a history of fitting or convulsions, and those taking anti-coagulant medicines (such as warfarin) were excluded from giving a blood sample. Full details of the response to the blood samples in 2008 and 2009, including the proportion of valid measurements obtained for each analyte, can be found in Volume 2 of this report.
9.2.2 Summary measures of cardiovascular disease and diabetes
Any CVD condition / Any CVD condition or diabetes
Participants were classified as having any CVD condition if they reported ever having any of the following conditions confirmed by a doctor: angina, heart attack, stroke, heart murmur, abnormal heart rhythm, or 'other heart trouble'. 20 A second definition that includes diabetes as well as the above CVD conditions is also presented in the tables as 'any CVD condition or diabetes' so that the total prevalence of these conditions can be seen. The trend table reports the prevalence of any CVD, and any CVD or diabetes, in 1995, 1998, 2003, 2008 and 2009.
Ischaemic heart disease
Participants were classified as having IHD if they reported ever having angina, or a heart attack, confirmed by a doctor.
Ischaemic heart disease or stoke
Participants were classified as having IHD or stroke if they reported ever having angina, or a heart attack, or a stroke, confirmed by a doctor.
9.2.3 Classification of blood pressure levels
The most recent guidelines from the British Hypertension Society state that antihypertensive therapy should be initiated in people with sustained levels of systolic blood pressure ( SBP) >160 mmHg or diastolic blood pressure ( DBP) >100 mmHg; and that in people with levels of SBP between 140 and 159 mmHg and/or DBP between 90 and 99 mmHg, treatment should be decided on the basis of presence or absence of CVD, diabetes, other target organ damage (e.g. kidney), or an estimated CVD risk = 20% over 10 years. 21 The most recent guidance from SIGN concurs with the guidance for treating those with existing or high risk of CVD, 22 while separate SIGN guidance recommends the use of antihypertensive medication for people with a previous stroke or transient ischaemic attack ( TIA, like a stroke but lasting less than 24 hours) regardless of BP level. 23
These guidelines are not universally accepted 24. For example, the United States uses guidelines that are more restrictive so that 140/90 mmHg (irrespective of risk factor) is considered the threshold for treatment and target to achieve. 25 In 2003 the European Society of Hypertension and the European Society of Cardiology jointly recommended a threshold of 140/90 mmHg in general and 130/80 mmHg for those with diabetes. 26
This report continues to use the blood pressure definition that was introduced in the 1998 survey (140/90 mmHg), in accordance with the British Hypertension Society guidelines. 21
Adult participants were classified into one of four groups on the basis of their systolic ( SBP) and diastolic ( DBP) blood pressure and current use of anti-hypertensive medications as follows:
SBP<140 mmHg and DBP<90 mmHg, not currently taking any drug specifically prescribed to treat high blood pressure
SBP<140 mmHg and DBP<90 mmHg, currently taking a drug specifically prescribed to treat high blood pressure
SBP³ 140 mmHg or DBP³ 90 mmHg, currently taking a drug specifically prescribed to treat high blood pressure
SBP³ 140 mmHg or DBP³ 90 mmHg, not currently taking a drug specifically prescribed to treat high blood pressure
For the purpose of this report, the term 'hypertensive' is applied to those in the last three categories.
9.2.4 Blood analytes
Glycated haemoglobin (HbA 1C) reflects the level of glucose in the blood over the preceding two to three months, and is therefore a better indicator of diabetic control than a random glucose sample, that is affected by recent food or drink intake. Elevated glycated haemoglobin in people without diabetes is associated with increased mortality following acute myocardial infarction. 27 Levels rise in people with undiagnosed diabetes. In June 2009, an international expert committee recommended using levels of 6.5% or more to diagnose diabetes. 28 Levels of 5.7% or more have been proposed as a screening test for diabetes. 29 However, neither has yet been accepted within Scotland or the UK.
The latest SIGN guidelines for diabetes sets <7% as the HbA 1C target for good glycaemic control in people with diabetes, 9 consistent with indicator DM 23 within the Quality and Outcomes Framework ( QOF) for 2009/2010. DM 23, which replaces DM 20, gives GPs the target of 40-50% of their diabetic patients having HbA 1C <7%, a reduction from <7.5% within DM 20. 30,31 The Task Force on Diabetes and Cardiovascular Diseases of the European Society of Cardiology ( ESC) and of the European Association for the Study of Diabetes ( EASD) recommends that HbA 1C be kept <6.5% to reduce cardiovascular risk. 32 For the purpose of this survey, a glycated haemoglobin value of 6.5% or above in people with no existing diabetes diagnosis was taken to indicate possible undiagnosed diabetes. The sample size for people with a diabetes diagnosis is too small to assess whether their condition is being adequately controlled so the chapter only looks at people with no such diagnosis.
Prospective studies have identified an increased risk of coronary disease associated with raised cholesterol concentration. A meta-analysis of all randomised trials of more than two years duration showed that lowering serum cholesterol confers clinical benefit as expressed in lower CHD mortality and total mortality risk, with the magnitude of benefit directly related to the degree of cholesterol reduction. 33 For the purpose of this survey cholesterol was considered to be raised at a level of 5.0 mmol/l or over. In 2000 the National Service Framework for Coronary Heart Disease suggested a total cholesterol target below 5.0 mmol/l for all patients with arterial heart disease or significant cardiovascular risk. 34 The QOF target for GPs relates to the percentage of patients with coronary heart disease whose total cholesterol is 5.0 mmol/l or below. 35 In 2005, the recommendations for defining and treating hypercholesterolaemia were superseded by the second guidance from the Joint British Societies, JBS2 .36 European guidance is based on assessing cardiovascular risk, using the SCORE tool, 37 while in Scotland the ASSIGN risk assessment tool has been developed to take better account of the risks associated with social deprivation and family history of CVD. 22SIGN Guidance advises the use of statins in people with pre-existing cardiovascular disease, diabetes, or estimated 10-year CVD risk of 20% or above, regardless of cholesterol level, or in those with total cholesterol of 8.0mmol/l or above. 9, 22, 23 The Scottish Government's 2009 Better Heart Disease and Stroke Care Action Plan also covers Familial Hypercholesterolaemia, a genetic condition in which affected people have very high cholesterol levels and high risk of premature cardiovascular disease. 4
High-density lipoprotein cholesterol
Studies have shown that high-density lipoprotein cholesterol ( HDL-cholesterol) is inversely and independently associated with the risk of developing CHD. 38,39 Furthermore, low levels of HDL-cholesterol are associated with a worse prognosis after myocardial infarction. 40 Protection against CVD by HDL-cholesterol is conferred in at least two ways. The first is that it transports cholesterol back from organs such as arteries to the liver for elimination, thus protecting the arteries from further atheromatous plaque formation. The second is by acting as an antioxidant. Increasing physical activity, decreasing alcohol intake, quitting cigarette smoking and losing weight can elevate HDL-cholesterol. Attention is generally recommended for HDL-cholesterol concentrations <1 mmol/l.
C-reactive protein ( CRP) is an acute-phase reactant which is synthesized in the liver in response to the pro-inflammatory protein interleukin 6 ( IL-6). It is therefore a sensitive marker of inflammation. Levels of these acute phase proteins have been related to risk of coronary heart disease ( CHD). Elevated levels of CRP are associated with increased risk of myocardial infarction ( MI) or sudden death among those with stable and unstable angina pectoris, 41 as well as with coronary heart disease in the elderly and coronary mortality among high-risk patients. The follow-up of the Multiple Risk Factor Intervention Trial ( MRFIT) has documented a strong relationship between levels of CRP and subsequent risk of CHD deaths among cigarette smokers. 42 However, it is more likely that these associations are due to confounding, with CRP unlikely to be causally related to CHD. 43 Although an American study raised the possibility that assessment of CRP may also provide a method of determining risk of future MI among apparently low-risk individuals, including non-smokers, 44 a review in 31 studies found that CRP was generally no more effective than the classical Framingham score in predicting CHD. 45 In the US, the first set of guidelines endorsing use of high-specificity CRP (hs CRP) in risk factor screening for CVD were produced in 2003, 46 but CRP is not currently included in screening in the UK, 36 nor is there a recommended CRP threshold in the UK.
9.3 PREVALENCE OF CARDIOVASCULAR CONDITIONS AND DIABETES
This section reports findings from the 1995, 1998, 2003, 2008 and 2009 Scottish Health Surveys. It examines the trend over time in the prevalence of: any CVD, any CVD or diabetes, IHD, stroke, and IHD or stroke. Changes to the sample composition over the first three survey years mean that the total figures presented for adults between 1995 and 2009 are for those aged 16-64, the trend for all adults aged 16 and over is also shown for 2003 onwards.
The 2009 prevalence figures for men and women, for each of these conditions, are shown in Table 9.1 and are summarised below. The prevalence of any CVD or diabetes, IHD, and IHD or stroke was significantly higher for men than for women. Prevalence of all these conditions increased markedly with age. For example, rates of any CVD, and any CVD or diabetes were below 5% for men aged under 35, and women under 25, whereas more than half of men, and around four in ten women aged 75 and over had these conditions. Table 9.1
IHD or stroke
Any CVD or diabetes
9.3.1 Any CVD, and CVD or diabetes, 1995, 1998, 2003, 2008, 2009
The prevalence of any CVD in men aged 16-64 was 8.4% in 1995, 8.1% in 1998 and then increased to 9.7% in 2003 and has been fairly static since then (9.9% in 2008 and 9.5% in 2009). Among women aged 16-64 prevalence ranged between 8.5% and 8.9% between 1995 and 2003. More recently, it was 10.7% in 2008 and 9.0% in 2009. The overall pattern between 1995 and 2009 therefore appears to suggest trendless fluctuation, with a possible outlier in 2008.
In contrast, the prevalence of CVD or diabetes among men has now increased in every survey year, from 9.4% in 1995, to 9.7% in 1998, 11.1% in 2003, 12.2% in 2008 and to 12.6% in 2009. The statistically significant increase between 1995 and 2009 in the prevalence of CVD or diabetes is largely accounted for by increasing levels of diabetes over time. However, it is not possible to conclude the extent to which this trend represents an overall increase in the incidence of CVD and/or diabetes among men or improved diagnostic or survival rates for these conditions. As shown in Chapter 7, levels of obesity have increased in this period which will have contributed to an increased incidence of type 2 diabetes.
The prevalence of any CVD or diabetes among women followed a similar pattern to that for any CVD; the rate ranged from 9.6% to 10.2% in the three earlier surveys, was higher in 2008 (12.8%), and lower again in 2009 (11.1%). Table 9.1
9.3.2 IHD, stroke, and IHD or stroke, 1995, 1998, 2003, 2008, 2009
The prevalence of IHD among men aged 16-64 has been similar across all survey years (ranging between 3.2% and 4.1%) with no significant trend. The same was true for stroke (ranging between 0.7% and 1.2%) and IHD or stroke (4.2%-5.0%). For women aged 16-64 there has been a slight decrease in IHD over time (from 2.9% in 1995 to 1.9% in 2009). Prevalence of IHD or stroke among women of this age was consistent over time (ranging between 2.4% and 3.2%). The slight increase in stroke prevalence noted last year (from 0.5% in 1995 to 1.2% in 2008), does not appear to represent a clear pattern as the prevalence in 2009 was 0.9%. Table 9.1
9.3.3 Diagnosed diabetes
Doctor diagnosed diabetes was estimated in both 2008 and 2009. However, to explore this in more detail, data from both years have been combined to provide a larger sample. This means that the estimates for men, women and different age groups are more precise.
In 2008/2009, 5.0% of adults aged 16 and over reported that they had been diagnosed by a doctor as having type 1 or type 2 diabetes; this was more common in men (5.7%) than women (4.3%). However, below the age of 45, women had slightly higher prevalence rates than men. Prevalence of doctor-diagnosed diabetes increased with age, most notably from the age of 45 in men and from the age of 55 in women. 5.7% of men and 3.2% of women aged 45-54 had doctor diagnosed diabetes compared with 14.2% of men and 9.9% of women aged 75 and over.
The prevalence of doctor-diagnosed diabetes in men and women has increased significantly over time. Between 1995 and 2008/2009 prevalence increased among those aged 16-64 from 1.5% to 4.0% in men and from 1.5% to 2.9% in women. When all adults aged 16 and over were considered there also appeared to have been a significant increase since 2003 in doctor-diagnosed diabetes among men. In 2003, 3.8% of men aged 16 and over had doctor-diagnosed diabetes compared with 5.7% in 2008/2009. The difference between the corresponding figures for women (3.7% and 4.3%, respectively) was not significant.
The 2008/2009 estimates of doctor-diagnosed diabetes reported here are very similar to those in the 2009 Scottish Diabetes Survey. This estimated the prevalence to be 5.0% in men and 3.8% in women (4.4% of all adults, equating to 228,004 people). 47 Of these, 87% had type 2 and 12% type 1 diabetes. Both the Scottish Health Survey and the Scottish Diabetes Survey estimates are higher than the QOF prevalence estimate for 2008/09 of 3.9%. 48 However, there are known problems with comparing QOF prevalence estimates with other sources. 49Table 9.2
9.3.4 Possible undiagnosed diabetes
In 2008/2009 2.5% of adults aged 16 and over (2.9% of men and 2.0% of women) without a diagnosis of diabetes had glycated haemoglobin levels of 6.5% or above, indicative of possible undiagnosed diabetes. The highest prevalence was in those aged 65-74: 9.0% of men and 7.9% of women without a diabetes diagnosis had raised glycated haemoglobin levels.
Glycated haemoglobin was first measured in the survey 2003 when the prevalence of raised levels was 1.1% overall (1.2% for men and 1.0% for women). The 2008/2009 figures therefore suggest at least a two-fold increase in prevalence of raised glycated haemoglobin in both sexes since 2003, which was statistically significant. The increased prevalence in 2008/2009 was due to higher percentages of men aged 35-74, and women aged 65 and over, exceeding the 6.5% glycated haemoglobin threshold. No adults aged under 35 without a diagnosis of diabetes had a raised glycated haemoglobin level in either 2003 or 2008/2009. For each of the older age groups the percentage with raised glycated haemoglobin was higher in 2008/2009 than in 2003. Table 9.3
9.4.1 Blood pressure level
Table 9.4 presents the four levels used to classify hypertension. They distinguish between people with normal blood pressure who are not receiving any treatment for hypertension, and those with normal levels who are taking anti-hypertensive medication. They also distinguish between people with raised blood pressure who are receiving treatment, and those who are not. These latter two categories are important target groups in the population. The first includes people with poorly managed hypertension, and the second provides an estimate of the prevalence of potentially undiagnosed cases of this condition. It should be noted, when considering this last category, that not everyone with a one-off raised blood pressure measurement actually has hypertension on repeated measurement; the definition of hypertension is 'sustained raised BP'. Nor does everyone with BP 140-159/90-99mmHg warrant treatment, which is indicated for people with existing CVD, diabetes, damage from raised blood pressure (e.g. kidney disease), or at high risk of developing CVD.
Hypertension in 2008/2009
Looking first at all forms of hypertension (blood pressure of ³ 140/90 mmHg, or taking anti-hypertensive medication), in 2008/2009 34.6% of men and 30.4% of women aged 16 and over were hypertensive. With the exception of the 75 and over age group (where rates were similar), men were more likely than women to have hypertension in every age category; the difference was most notable in those under 35. Hypertension increased with age for both sexes. In women, the prevalence was relatively low in the younger age groups (1.5%-5.7%), and increased sharply for those aged 34-44 (11.2%) and 45-54 (30.2%). This was followed by a more than two-fold increase between the 45-54 and 65-74 age groups to 67.0%, and was similar in the oldest age category (70.2%). In men, rates were higher in the younger age groups than they were for women (12.4%-14.5%), but the increase with age followed the same general pattern. The most notable increase in rates of hypertension for men was observed between those aged 45-54 (32.4%) and 55-64 (52.4%), before peaking in the two oldest age groups (70.7% and 67.5%). Table 9.4, Figure 9A
Untreated hypertension was found in 20.1% of men and 14.3% of women aged 16 and over, which, as noted in Section 9.4.1, is a possible indicator of the level of undiagnosed hypertension in the population. For men under 45 and women under 55, untreated hypertension was far more common than controlled or uncontrolled hypertension. Untreated hypertension generally increased with age, and was highest in both men and women aged 55 and over. In men, the highest prevalence of untreated hypertension was found in those aged 75 and over (29.5%). Among women, the rates were highest in those aged 65-74 (26.6%).
The rates of successful and unsuccessful hypertension control were similar to each other. 8.3% of men and 8.2% of women had controlled hypertension (i.e. had a normal blood pressure level), 6.2% of men and 7.9% of women had uncontrolled hypertension, despite taking anti-hypertensive medication. Both increased with age, and around a fifth of men aged 55 and over, and women aged 65 and over, had controlled hypertension. Rates of uncontrolled hypertension were also highest in the oldest age groups (around a fifth), though women aged 75 and over had higher rates of this (28.8%). Table 9.4
Trends in hypertension 1998, 2003 and 2008/2009
This section compares blood pressure levels in 1998, 2003 and 2008/2009. Blood pressure categories use information about prescribed medications. As questions about medications were first included in SHeS in 1998 the trends in blood pressure levels exclude 1995. As adults aged 75 and over were not included in the 1998 survey the figures presented here are based on those aged 16-74. Table 9.4 also includes figures for adults aged 16 and over for 2003 and 2008/2009.
There has been an increase in the prevalence of hypertension among men aged 16-74 since 1998 (from 22.3% to 32.1% in 2008/2009). However, the rates in 2008/2009 and 2003 (29.5%) were not significantly different, which might suggest that the rate of increase has slowed or levelled off. Later figures in the series, for example from 2010/2011, will help to confirm whether this is the case. It is also worth noting, as the 2003 Report did, that the change in the measurement equipment used between 1998 and 2003 might have contributed to some of the increase in hypertension. 19
The same pattern was observed among women; although the increase since 1998 was smaller than it was for men, it was significant. In 1998, 21.2% of women aged 16-74 had hypertension compared with 26.7% in 2003 and 25.9% in 2008/2009.
The prevalence of successfully controlled hypertension among men aged 16-74 has increased steadily and significantly from 3.0% in 1998, to 5.3% in 2003, and to the current prevalence of 7.4%. The corresponding figures for women were 4.4%, 6.0% and 6.7%, respectively, which was also a significant increase.
The small increase in controlled hypertension among men has not been accompanied by falls in the levels of uncontrolled or untreated hypertension. Both of these have increased very slightly since 1998, though in both cases the 2003 and 2008/2009 figures were fairly close. For example, 15.6% of men aged 16-74 in 1998 had untreated hypertension, compared with 19.6% in 2003 and 19.3% in 2008/2009. As with the other categories, rates of untreated hypertension among women aged 16-74 have seen smaller changes over time (from 12.8% in 1998, to 14.8% in 2003 and 13.6% in 2008/2009). Table 9.4
9.4.2 Systolic blood pressure ( SBP)
Table 9.5 shows mean blood pressure levels. Mean SBP was 130.3 mmHg in men and 125.5 mmHg in women aged 16 and over. Mean SBP was higher in men than in women under the age of 65, but was slightly higher among women from the age of 65. Mean SBP increased with age, with the highest levels for both sexes found in those aged 65-74 (137.9 mmHg for men, 140.4 mmHg for women). Mean SBP then decreased slightly in those aged 75 and over.
Table 9.5 also compares mean SBP in 1995, 1998, 2003 and 2008/2009, for adults aged 16-64. Mean SBP in both sexes has been broadly similar in every survey year. Indeed, mean SBP was identical in 1995 and 2008/2009 for women aged 16-64 (121.7 mmHg), and was almost the same for men (128.3 and 128.7 mmHg, respectively). Table 9.5
9.4.3 Diastolic blood pressure ( DBP)
Mean DBP was almost identical in both sexes aged 16 and over (73.8 mmHg in men and 73.9 mmHg in women). Among men, mean DBP rose from 65.3 mmHg in those aged 16-24 to 78.0 mmHg in those aged 45-54, before decreasing steadily to 68.8 mmHg in those aged 75 and over. Among women the mean DBP increased from 70.3 mmHg in those aged 16-24 and then peaked in those aged 55-64, before decreasing to 68.6 mmHg in those aged 75 and over.
There was an increase in mean DBP among men aged 16-64 between 1995 (72.9 mmHg) and 2003 (74.6 mmHg), but the figure for 2008/2009 (74.2 mmHg) was very similar. Mean DBP in women aged 16-64 has increased slightly between each survey year, from 69.6 mmHg in 1995, to 70.5 mmHg in 1998, 73.5 mmHg in 2003, and 74.6 mmHg in 2008/2009. The differences in mean DBP between 1995 and 2008/2009 for both sexes were statistically significant. Table 9.5
9.5 FACTORS ASSOCIATED WITH CVD, IHD, ANDSTROKE
9.5.1 Prevalence of risk factors amongst those with and without CVD conditions
This section presents the prevalence of a range of behavioural, biological and socio-economic risk factors known to be associated with CVD, separately for those with and without any CVD conditions (using the same definition as in Table 9.1). The figures in Table 9.6 are based on the 2008 and 2009 surveys combined. Many of the risk factors explored here are used in the risk assessment frameworks such as ASSIGN and Framingham.
The risk factors included in this analysis were as follows:
- Being a current cigarette smoker
- Being an ex-regular cigarette smoker
- Drinking in excess of weekly recommendations (14 units for women, 21 for men)
- Being physically inactive
- Overweight and obesity ( BMI 25 kg/m 2 and above)
- Family history of CVD (death of a parent from a CVD condition before the age of 65)
- NS-SEC semi-routine or routine group
- Equivalised household income in the lowest quintile
- SIMD: lowest quintile and most deprived 15% of areas
- Blood pressure of =140/90 mmHg (regardless of treatment status)
- Doctor-diagnosed diabetes (excluding diabetes in pregnancy)
- Raised total cholesterol (= 5.0 mmol/l)
- Low HDL-cholesterol (<1 mmol/l)
- C-reactive protein level in the highest quintile
All these risk factors are known to be associated with CVD. Given that they are recognised risk factors, one might expect to find a higher prevalence of these among those with CVD than in people without the disease. However, as these data come from a cross-sectional survey conducted at one point in time, it is not possible to assess the direction of the association between these factors. In some cases, a lower prevalence of risk factors among people with CVD may, at least in part, be attributable to a diagnosis of CVD being followed by behavioural changes or medication. It is also possible that people with these risk factors may have been more at risk of dying than those without, leaving a residual CVD population with lower than average prevalence of these risk factors.
Smoking, alcohol consumption and physical activity
Smoking prevalence was more common among those without CVD than with, though the differences between the groups varied for men and women. For example, 26.8% of men without CVD were current smokers compared with 22.2% with CVD, whereas the equivalent rates for women were almost identical in the two CVD groups (24.9% without CVD and 23.8% with CVD). One possible explanation for this difference is that some people change their smoking behaviour after diagnosis. One way of exploring whether this is the case is to compare the rates of ex-regular smoking in people with CVD and without CVD. Those with CVD were much more likely than those without the disease to be an ex-regular smoker and this was especially true for men. 42.4% of men with CVD were ex-regular smokers compared with 20.9% of men without CVD. The corresponding figures for women were 28.5% and 19.8%, respectively. Table 9.6
Consuming alcohol in excess of weekly recommendations was more common among those without CVD than with, though the differences between the groups varied for men and women. In contrast, while men without CVD were more likely than those with to drink more than 21 units a week (29.6% versus 22.4%), the corresponding difference between women who drank more than 14 units was larger (20.8% versus 11.0%). It is likely that people who have been diagnosed with CVD will have had to make alterations to their smoking or drinking habits as a result of their condition.
Low activity levels were much more common in men and women with CVD than those without. Among men, 50.6% with CVD were inactive compared with 25.3% of those without. The corresponding figures for women were 53.1% and 30.0%, respectively. Almost two-thirds of men and almost three-quarters of women with CVD aged 65 and over were inactive compared with around half of those in the same age group without CVD. People who are physically inactive are at twice the risk of developing CVD as those who meet recommended levels of activity. Some people with CVD conditions may increase their levels of activity after receiving their diagnosis but others would become less active either due to concern or because symptoms of angina, pain in the legs on exercising, or breathlessness prevents exercise. Table 9.6
Overweight and obesity
Both men and women with CVD had a higher prevalence of overweight or obesity ( BMI of 25 kg/m 2 and above) than men and women without CVD. Among men, 77.6% of those with CVD were overweight or obese, compared with 66.5% of those without CVD. The corresponding figures for women were 68.8% and 60.2%, respectively. This might reflect the fact that obesity is a risk factor for CVD, or could be related to the above point that inactivity is more likely after a diagnosis of CVD (which could contribute to weight gain post CVD onset). Table 9.6
Both men and women with a family history of CVD (defined as one or both parents dying of CVD before the age of 65) were more likely to have CVD when compared with those without such a history. 17.0% of men with CVD compared with 9.8% without had a family history of CVD. The corresponding figures for women were similar, 17.7% and 11.8% respectively. Among men, this increased prevalence of family history of CVD in those with a diagnosis of CVD was observed in all age groups, but was most marked in those aged 16-64. In women the difference between those aged 45-64 was bigger than for the younger and older age groups. Table 9.6
Hypertension and diabetes
Hypertension was associated with being diagnosed with CVD in both men and women. 33.6% and 30.2% of men and women with CVD respectively had hypertension, compared with 24.8% and 20.7% of men and women without CVD. This is unsurprising, as a major indication for anti-hypertensive treatment is having existing CVD, so those with CVD are more likely to have their blood pressure checked and also to have raised levels treated.
There was a four-fold increase in men, and a three-fold increase in women, of having diabetes in the CVD group compared with those without CVD. 15.2% of men and 10.5% of women with CVD had diabetes compared with 4.0% and 3.2% of men and women without CVD respectively. Similarly, in addition to the increased CVD risk among people with diabetes, people with CVD are more likely to be tested for diabetes. Table 9.6
Blood lipids and c-reactive protein
Although the sample sizes are too small to look at the levels across different age groups, and the estimates for men and women with CVD will have wide confidence intervals, the overall patterns are generally clear. The prevalence of raised total cholesterol was lower in men and women with CVD than those without. This was much more marked among men: 32.9% of those with CVD had raised cholesterol compared with 60.5% without CVD. The corresponding figures for women were 56.5% and 62.3%, respectively. This decreased prevalence of raised cholesterol is most likely due to being prescribed drugs such as statins as well as, to a lesser extent, a change of diet after receiving a diagnosis of CVD. The equivalent analysis in 2003 also found the difference between those with and without CVD to be greater for men than women, however the size of the difference among men with and without CVD was greater in 2008/2009 than it was in 2003. This is most likely to be due to an increase in the use of statins since 2003, as has been seen in England, 50 probably in response to the QOF initiative, but a more detailed investigation than has been possible here must be carried out before such conclusions can be drawn.
Men with CVD had a higher prevalence of low HDL-cholesterol than those without CVD (19.0% compared with 8.1%). There was little difference in low HDL-cholesterol prevalence among women with and without CVD (3.3% and 2.7% respectively).
There was also an increased prevalence of high CRP in men with CVD compared with those without CVD (33.0% versus 17.7%). Women's CRP levels did not differ greatly between the two groups (22.8% versus 18.4%). Table 9.6
NS-SEC, income and deprivation
All the socio-economic risk factors had a higher prevalence in those with CVD compared with those without CVD. Men and women with CVD were more likely to live in semi-routine or routine households than those without CVD (50.0% versus 41.4% for men, 48.3% versus 40.7% for women). Similarly, men and women with CVD were more likely to be living in the lowest income quintile households, and in the most deprived areas, than those without. In each case, the difference between those with and without CVD was most marked in the 45-64 age group. For example, among men aged 45-64, 24.7% of those with CVD lived in the most deprived SIMD quintile compared with 15.7% of men of the same age without CVD. Whereas, the gap between men overall was quite small (21.0% versus 17.3%). This reflects the fact that those in worse socio-economic circumstances tend to develop, and die from, CVD at younger ages than their peers in more advantageous circumstances. Table 9.6
9.5.2 Prevalence of risk factors amongst those with and without IHD or stroke
This section repeats the same form of analysis as described above for any CVD, and looks at ischaemic heart disease and stroke, which are severe manifestations of CVD. As was mentioned in the previous section, caution is needed when interpreting the results as people with IHD or stroke may have amended their behaviours as a result of becoming ill and/or receiving such a diagnosis, may have been tested for additional diagnoses, such as hypertension or diabetes, and/or may be taking medication as a result of the diagnosis, such as statins or anti-hypertensive medication. Also note that the sample size for adults under 45 with IHD or stroke is very small so estimates are not presented here. Similarly, the sample size for those providing a valid blood sample and who had IHD or stroke is too small to permit comparisons for blood lipid and CRP levels.
Table 9.7 generally shows similar patterns to those shown for any CVD condition in Table 9.6. For example, the prevalence of exceeding weekly alcohol limits among both sexes is higher in those without IHD or stroke than those with these conditions. Conversely, low activity levels, being overweight or obese, and prevalence of diabetes, hypertension and a family history of CVD are all higher among those with IHD or stroke. It is notable that men and women aged 45-64 with IHD or stroke continued to be more likely to smoke after their diagnosis than those in the same age group without a diagnosis. The socio-economic risk factors were all associated with having IHD or stroke, with the differences between groups generally larger than was the case for any CVD. For example, 57.3% of men and 62.6% of women with IHD or stroke lived in semi-routine or routine households, compared with 41.2% of men and 40.3% of women without IHD or stroke. As with any CVD, socio-economic differences were the most notable in the 45-64 age group. Table 9.7
9.6 MULTI-VARIABLE ANALYSIS OF FACTORS ASSOCIATED WITH ANY CVD
Logistic regression was used to estimate the independent effect of a range of factors associated with any CVD condition after each one had been adjusted for simultaneously. The factors investigated in the regression included a number of the behavioural characteristics explored in other chapters in this report, such as cigarette smoking, physical activity, alcohol consumption (drinking in excess of recommended weekly limits) and BMI, as well as the key socio-demographic factors of age, SIMD quintile, equivalised household income and both parental and household NS-SEC. Three additional factors of interest to CVD were also included: diabetes, family history of CVD and total cholesterol. Although data on other blood results ( HDL cholesterol, fibrinogen and C-reactive protein) and hypertension is also now available from two years of nurse visits, given that the missing values (i.e. those who did not participate in a nurse interview) for these largely overlap, the decision was taken to include only one of these variables in the regression model, in order to avoid problems relating to co-linearity. The regression was run separately for men and women using combined data for 2008 and 2009. 51 The factors found to be significant are discussed below. For more information about logistic regression models and how to interpret their results see the Glossary at the end of this volume.
The odds ratios of having any CVD condition among selected sub-groups for men and women are shown in Table 9.8. An odds ratio of less than one means that the odds of a given group having CVD are lower than that of the reference group. An odds ratio of greater than one means that the odds of that group having CVD are higher than for the reference group. Independent variables with a 'p' value of 0.05 or less are significant predictors of the dependent variable at the 95% confidence level. Reflecting the findings reported above, the odds of reporting any CVD condition increased significantly with age from 45 years onwards, with men and women over the age of 75 years having the highest odds of having CVD (12.8 and 6.2 respectively) compared with the reference category (those aged 16-24).
Area deprivation (as measured by SIMD quintiles) was significant for men, with those in the most deprived areas having higher odds of CVD than those in the least deprived. Although a similar pattern by SIMD was apparent in the odds for women, overall SIMD was not statistically significant in the model for women. Overall, equivalised household income was significantly associated with having CVD for women only, but the nature of the relationship was not clear.
A number of lifestyle factors were significantly associated with having higher odds of CVD. For both men and women, those who were ex-regular smokers had higher odds of having CVD (1.5 for men and 1.3 for women) than those who had never smoked. Weekly alcohol consumption was significant for women but not men, with women who consumed more than the recommended weekly limit having lower odds of CVD (0.7) than those whose consumption was within recommended weekly limits. Similar findings on smoking and alcohol consumption were found in the similar analysis presented in the 2003 Report, and in previous Health Survey for England analyses. They may reflect the fact that people may make changes to their lifestyle - such as giving up smoking and cutting down on alcohol - after a cardiovascular episode or diagnosis.
Low levels of physical activity were significantly associated with CVD for both men and women. Compared with those with high levels of physical activity (30 minutes a day on 5 or more days a week), the odds of men with low levels of physical activity (fewer than 30 minutes of moderate activity per week) having CVD were 1.4 times higher. For women, the odds were 1.7 times higher. As discussed in section 9.5.1 above, it is not possible from this cross-sectional data to ascertain the direction of the relationship between CVD and physical activity. It may be that some people with a diagnosis of CVD decrease their level of physical activity as a result. However, being physically active has been shown to contribute to a decreased likelihood of developing CVD over a lifetime. 52,53,54,55
Having doctor-diagnosed diabetes, shown to be a risk factor above, was associated with higher odds of having CVD even after other factors are controlled for. Men with diabetes had odds of 1.8 and women with diabetes odds of 1.9 compared with those without diabetes.
Finally, total cholesterol was significantly associated with the odds of having CVD. Men and women with raised cholesterol levels, of 5 mmol/litre or more have lower odds of having CVD than do those with lower cholesterol levels. As discussed above, this somewhat counter-intuitive finding, which has been replicated in earlier Scottish Health Surveys and in the Health Survey for England, reflects the fact that people with a diagnosis of CVD are now much more likely to be prescribed cholesterol lowering drugs (e.g. statins) than are people without CVD. Table 9.8