2. Morbidity. Incidence

Transcription

1 2. Morbidity This chapter reports on country-level estimates of incidence, case fatality and prevalence of the following conditions: myocardial infarction (heart attack), stroke, angina and heart failure. Additional estimates for coronary heart disease (CHD) and cardiovascular disease (CVD) are provided where possible. Measuring the morbidity of a disease is much more complicated than counting the number of deaths that have occurred due to a disease. For example, people may be suffering from a disease and not be aware of it or the exact time of onset of disease may not be known. As such, the estimates provided in this chapter should be treated with more caution than those from chapter one, yet they represent the best available estimates of the morbidity from CHD for countries within the UK. The estimates provided in this chapter are drawn from a number of different data sources, including samples of GP registers, hospital episode and mortality statistics and national survey data, each of which have their own strengths and limitations. Incidence Incidence of myocardial infarction has decreased in a number of developed countries during the past three decades, including the UK, driven by favourable changes in risk factors. The most recent estimates of incidence of myocardial infarction in the UK are based on national-level data from linked hospital and mortality statistics, and they suggest that in Scotland the incidence rate of myocardial infarction has decreased by about 25% between 2000 and 2009 in both men and women (Table 2.1). In general, incidence of myocardial infarction increases sharply with age. Incidence is also higher in men than in women but the difference between sexes decreases with increasing age 1. For the years in which comparison can be made (2005 to 2007), incidence of myocardial infarction appears to be between 20% and 35% higher in Scotland compared to England for both men and women, suggesting a considerable North-South gradient in the UK (Table 2.1 and Figure 2.1). Using the most recent data available from Scotland and England, we estimate that there are around 62,000 heart attacks in English men and 39,000 in English women every year, and 8,000 heart attacks in Scottish men and 5,000 in Scottish women every year. If the rates of heart attack in Wales and Northern Ireland were comparable to that in England, then there would be approximately 124,000 heart attacks in the UK every year (Table 2.1 and Figure 2.1). Similarly to rates of myocardial infarction, incidence of stroke has decreased in many developed countries during the past three decades, including the UK. On average around the world, stroke occurs around 30% more often in men than in women but the difference between sexes decreases with increasing age 2. Data from the South London Stroke Register suggest that stroke incidence decreased by 18% in men and by 24% in women from 1995/96 to 2003/04 3, while the Oxford Vascular Study reported a 40% reduction in stroke incidence over the past two decades 4,5. Recent national-level data from England and Scotland also show that stroke incidence rates are around 25% higher in men than in women and increase with age. They also show that the incidence of stroke is higher in Scotland than in England, but the difference is not as large as for myocardial infarction (Table 2.2 and Figure 2.2). 42 Using the most recent data available from Scotland and England, we estimate that there are around 57,000 strokes in English men and 68,000 in English women every year, and 6,500 strokes in Scottish men and 8,000 in Scottish women every year. Despite higher incidence rates in men than in women, there are a

2 greater number of events in women because women tend to live longer than men. If the rates of stroke in Wales and Northern Ireland were comparable to that in England, then there would be approximately 152,000 strokes in the UK every year (Table 2.2). Estimates of the incidence of angina and heart failure can be provided from representative samples of GP registries. The General Practice Research Database (GPRD) contains anonymised records from such a sample in England, Wales, Scotland and Northern Ireland. GPRD data suggest that in 2009 the incidence rate of angina was the highest in Scotland and lowest in England for both men and women. Overall in the UK, incidence rates were 75% higher in men compared to women. Incidence rates generally increase with age, and are highest in the age group in both men and women. Using these incidence rates, we estimate there are nearly 28,000 new cases of angina in the UK every year (Table 2.3). Data from the GPRD were used to provide the most recent estimates of occurrence of heart failure in the UK. In 2009, incidence of heart failure was highest in Northern Ireland and lowest in England for both men and women. Overall in the UK, incidence rates of heart failure were about 60% higher in men compared to women. Incidence of heart failure increased with age and was highest in adults over 75 years. Using these incidence rates, we estimate there are over 27,000 new cases of heart failure in the UK every year (Table 2.4). Case fatality Estimates of case fatality for stroke and myocardial infarction that are included in this publication only include those who reach hospital alive, and hence do not include sudden out-of-hospital deaths from either condition. In England, around 11% of men and 15% of women who were admitted to hospital with myocardial infarction in 2006 had died within 30 days. Case fatality rates in Scotland in 2008 were higher, with 12% of men and 19% of women admitted with myocardial infarction dying within 30 days (Table 2.5). Case fatality from myocardial infarction increases with age and is higher in women than in men. However, this gender difference is largely a reflection of the different age distribution of the female patient population, with more elderly women surviving to be admitted for myocardial infarction compared to elderly men (Table 2.5). Case fatality rates for stroke are higher than for myocardial infarction, but are measured over a different time period (60 days rather than 30 days). In England, estimates based on linked hospital and mortality data show that about 17% of men and 25% of women admitted to hospital for stroke in 2006 died within 60 days. In Scotland, similar analyses show that 19% of men and 25% of women admitted to hospital for stroke in 2008 died within 60 days (Table 2.6). In both England and Scotland, case fatality rates for myocardial infarction and stroke were substantially lower in individuals under 75 years of age compared to the rate in all age groups (Tables 2.5 and 2.6). Prevalence The prevalence of cardiovascular conditions such as myocardial infarction, stroke and angina increases with age and is higher in men than in women. The most recent national survey data suggests that in comparison with the rest of the UK, the prevalence of previous myocardial infarction is highest in Wales, whilst the prevalence of angina is highest in Northern Ireland. However, the differences between countries are not very large (Tables 2.7 to 2.10 and Figures 2.10a, b and c). 43

3 Age- and sex-specific prevalence estimates from national surveys allow us to estimate the number of people living in the UK who have previously had a myocardial infarction or stroke, or are currently suffering from angina or coronary heart disease. Using these figures, we estimate that there are around 1 million men and nearly 500,000 women who have had a myocardial infarction, giving a total of over 1.5 million people. Over 900,000 of these people are under the age of 75. Using similar methods we estimate that nearly 600,000 men and women each in the UK have had a stroke, giving a total of nearly 1.2 million people. Around 600,000 of these people are less than 75 years of age. The prevalence of the chronic condition angina is higher than for the acute conditions of myocardial infarction and stroke the prevalence of angina is around 5% in men and 4% in women in the UK. There are around 1.2 million men and over 900,000 women in the UK suffering from angina, giving a total of nearly 2.1 million people. Over 1.2 million of these people are under the age of 75. The prevalence of CHD (which includes angina and myocardial infarction but not stroke or heart failure) in the UK increases with age and is higher in men than in women. There are over 1.6 million men in the UK with CHD and over 1 million women, giving a total of nearly 2.7 million people. Nearly 1.6 million of these people are less than 75 years of age (Tables 2.7 and 2.8). The GPRD can also be used to estimate the prevalence of angina and heart failure within the UK. Estimates for the prevalence of angina using the GPRD data are lower than estimates provided by national survey data. For example, the prevalence of angina in English men aged 75 and over is estimated as 16% using GPRD data but 23% using the Health Survey for England However, the prevalence rates of heart failure estimated by GPRD data and national survey data appear closer in Welsh men aged 75 and over, the prevalence is estimated as 13% using GPRD data and 9% using the Welsh Health Survey. These discrepancies illustrate the difficulties in interpreting morbidity data (Tables 2.11 and 2.12). However, the estimates derived from national survey data of the number of people in the UK who have CHD or have had a stroke (given above) are broadly supported by results from the Quality Outcomes Framework. This framework became part of general practice contracts in 2004, and rewards GPs for keeping up-to-date records of the number of patients within their practices who are suffering from certain conditions. Data from the Quality Outcomes Framework suggest that in 2008/09 there were around 2.3 million people suffering from CHD and 1.1 million people suffering from stroke. The prevalence of CHD was higher in Scotland (4.4%), Wales (4.2%) and Northern Ireland (4.1%) than in England (3.5%). Prevalence rates were also higher in the North of England than in the South. Prevalence rates for stroke follow a similar geographic pattern. Prevalence rates for CHD show a wide variation, with lowest rates in London (2.2%) and highest rates in the Western Isles of Scotland (6.1%). However, these rates have not been adjusted to account for differences in the age structure of populations, and so differences in rates should be treated with caution (Table 2.13). 44 Temporal trends in the prevalence of CHD and CVD can be estimated using data from national health surveys. The Health Survey for England series suggest that between 1994 and 2006 the prevalence of CHD increased from 6.0% to 6.5% in men and remained stable for women (from 4.1% in 1994 to 4.0% in 2006). An increase in the prevalence of CVD (defined here as either CHD or stroke) was also obtained in the Health Survey for England, increasing from 7.1% to 8.1% in men and from 5.2% to 5.6% in women between 1994 and These increases were found in the majority of age groups in both men and women, with the most consistent increase in trend found in the oldest age group (75 years and over) 6.

4 Age-specific prevalence rates for CVD have been measured since 1988 in the General Household Survey series. They suggest that, for men aged 45 and over, prevalence of CVD increased between 1988 and the mid-2000s, and may have been falling slightly since then. For women, prevalence rates in these age groups certainly peaked in the early to mid 2000s and have declined since. Prevalence rates in the older age groups are still higher than they were at the end of the 1980s. For men aged 65-74, prevalence rates peaked in 2003, when they were 40% higher than in 1988 equivalent rates in 2008 are 26% higher than in For women aged 65-74, prevalence rates in 2003 were 30% higher than in 1988, but rates in 2008 are very similar to 1988 rates (Table 2.14 and Figure 2.14). 1. Age-specific rates have been calculated but are not presented in this publication. 2. Appelros P, Stegmayr B, Terent A (2009). Sex differences in stroke epidemiology. A systematic review. Stroke, 40; Heuschmann P, Grieve A, Toschke A, Rudd A, Wolfe C (2008). Ethnic group disparities in 10-year trends in stroke incidence and vascular risk factors: The South London Stroke Register (SLSR). Stroke, 39: Rothwell P, Coull A, Giles M, Howard S, Silver L, Bull L, Gutnikov S, Edwards P, Mant D, Sackley C, Farmer A, Sandercock P, Dennis M, Warlow C, Bamford J, Anslow P (2004). Change in stroke incidence, mortality, case-fatality, severity and risk factors in Oxfordshire, UK, from 1981 to 2004 (Oxford Vascular Study). Lancet, 363 (9425): Scarborough P, Peto V, Bhatnagar P, Kaur A, Leal J, Luengo-Fernandez R, Gray A, Rayner M, Allender S (2009). Stroke Statistics. British Heart & The Stroke Association: London. 6. Joint Health Surveys Unit (2007). Health Survey for England The Information Centre: Leeds. 45

5 Table 2.1 Incidence of myocardial infarction by age and sex, 2000 to 2009, Scotland and 2005 to 2007, England Incidence rate per 100,000 SCOTLAND Number of events (most recent year) Under ,026 All ages ,971 Under ,087 All ages ,330 ENGLAND Under ,150 All ages ,233 Under ,345 All ages ,650 Incident cases include all mortalities and hospital admissions for myocardial infarction (ICD-10 I21-22) with no previous hospital admission for the same condition in the previous 30 days. Incident cases potentially include misdiagnoses and further investigation of earlier myocardial infarctions. Rates are age-standardised to the European Standard Population. Estimates for England are provisional, and may be updated in future publications. Unit of Health-Care Epidemiology, Department of Public Health, University of Oxford (2010) Personal communication. Information Services Division Scotland (2010) Personal communication. Figure 2.1 Incidence of myocardial infarction by age and sex, 2007, England and Scotland 300 Age-standardised incidence rate per 100, Scotland England 0 Men Women Men Women ALL AGES UNDER 75s 46

6 Table 2.2 Incidence of stroke by age and sex, 2000 to 2009, Scotland and 2005 to 2007, England Incidence rate per 100,000 SCOTLAND Number of events (most recent year) Under ,409 All ages ,532 Under ,673 All ages ,830 ENGLAND Under ,835 All ages ,488 Under ,047 All ages ,457 Incident cases include all mortalities and hospital admissions for stroke (ICD-10 I60-69) with no previous hospital admission for the same condition in the previous 60 days. Incident cases potentially include misdiagnoses and further investigation of earlier strokes. Rates are age-standardised to the European Standard Population. Estimates for England are provisional, and may be updated in future publications. Unit of Health-Care Epidemiology, Department of Public Health, University of Oxford (2010) Personal communication. Information Services Division Scotland (2010) Personal communication. Figure 2.2 Incidence of stroke by age and sex, 2007, England and Scotland 250 Age-standardised incidence rate per 100, Scotland England 0 Men Women Men Women All ages Under 75s 47

7 Table 2.3 Incidence of angina by sex and age, 2009, England, Scotland, Wales and Northern Ireland Incidence rate per 100,000 England Scotland Wales Northern Ireland United Kingdom All ages All ages Number of cases: 1, ,462 1, ,670 Estimates are based on records from a sample of general practices in each of the constituent countries of the United Kingdom. Incidence rates are provided per 100,000 person years, as opposed to per 100,000 persons per year. These two denominators are broadly comparable provided that mortality rates in the groups are reasonably low. Estimates for all ages are age-standardised to the European Standard Population. General Practice Research Database (2010) Personal communication. This table is based on data from the General Practice Research Database, Copyright and database rights over the data belong to the Crown. The interpretation and conclusions contained in this report are those of the authors alone. Table 2.4 Incidence of heart failure by sex and age, 2009, England, Scotland, Wales and Northern Ireland Incidence rate per 100,000 England Scotland Wales Northern Ireland United Kingdom All ages All ages Number of cases: 2, ,659 1, , Estimates are based on records from a sample of general practices in each of the constituent countries of the United Kingdom. Incidence rates are provided per 100,000 person years, as opposed to per 100,000 persons per year. These two denominators are broadly comparable provided that mortality rates in the groups are reasonably low. Estimates for all ages are age-standardised to the European Standard Population. General Practice Research Database (2010) Personal communication. This table is based on data from the General Practice Research Database, Copyright and database rights over the data belong to the Crown. The interpretation and conclusions contained in this report are those of the authors alone.

8 Table 2.5 SCOTLAND Case fatality rates of those admitted to hospital for myocardial infarction by age and sex, 2008 Scotland and 2006 England ENGLAND Under 30 days Under 30 days % % Under Under All ages 12.0 All ages 10.6 Under Under All ages 18.7 All ages 15.1 Number of events: Under Under 75 1,255 All ages 651 All ages 4,014 Under Under All ages 626 All ages 3,716 Incident cases include all hospital admissions for myocardial infarction (ICD-10 I21-22) with no previous admission for the same condition in the previous 30 days. All mortalities from any cause are included in the numerator. Estimates for England are provisional, and may be updated in future publications. Unit of Health-Care Epidemiology, Department of Public Health, University of Oxford (2010) Personal communication. Information Services Division Scotland (2010) Personal communication. Table 2.6 SCOTLAND Case fatality rates of those admitted to hospital for stroke by age and sex, 2008, Scotland and 2006, England ENGLAND Under 60 days Under 60 days % % Under Under All ages 18.7 All ages 17.1 Under Under All ages 25.2 All ages 24.7 Number of events: Under Under 75 2,404 All ages 1,009 All ages 7,615 Under Under 75 2,188 All ages 1,463 All ages 12,119 Incident cases include all hospital admissions for stroke (ICD-10 I60-69) with no previous admission for the same condition in the previous 60 days. All mortalities from any cause are included in the numerator. Estimates for England are provisional, and may be updated in future publications. Unit of Health-Care Epidemiology, Department of Public Health, University of Oxford (2010) Personal communication. Information Services Division Scotland (2010) Personal communication. 49

9 Table 2.7 Prevalence of CHD, stroke, myocardial infarction and angina by age and sex, 2006, England Having ever been diagnosed with: CHD Stroke Myocardial Angina CVD Unweighted infarction base % % % % % , , , All ages , , , , , All ages ,925 Prevalence rates are weighted for non-response. Respondents were prompted to recall whether they had ever been diagnosed with each of the conditions by a doctor. Joint Health Surveys Unit (2008). Health Survey for England 2006: Cardiovascular disease and risk factors. The Information Centre: Leeds. Table 2.8 Prevalence of CHD, stroke, myocardial infarction and angina by age and sex, 2008, Scotland Having ever been diagnosed with: CHD Stroke Myocardial Angina CVD Unweighted infarction base % % % % % All ages , All ages , Prevalence rates are weighted for non-response. Respondents were prompted to recall whether they had ever been diagnosed with each of the conditions by a doctor. Scottish Centre for Social Research (2009). Scottish Health Survey The Scottish Government: Edinburgh.

10 Table 2.9 Prevalence of any heart condition, stroke, myocardial infarction, angina and heart failure by age and sex, 2008, Wales Having ever been diagnosed with: Currently being treated for: Myocardial Stroke Angina Heart Any heart Unweighted infarction Failure condition base % % % % % , All ages , , , , All ages ,866 Prevalence rates are weighted for non-response. Respondents were prompted to recall whether they had ever been diagnosed with heart attack or stroke, and whether they are currently being treated for angina, heart failure or other heart conditions by a doctor. Prevalence of any heart condition includes heart failure and is hence not comparable with estimates of the prevalence of coronary heart disease. Welsh Assembly Government (2009). Welsh Health Survey Welsh Assembly Government: Cardiff. Table 2.10 Prevalence of stroke, myocardial infarction and angina by age and sex, 2005/06, Northern Ireland Having ever been diagnosed with: Stroke Myocardial infarction Angina Unweighted base % % % All ages , All ages ,497 Prevalence rates are weighted for non-response. Respondents were prompted to recall whether they had ever been diagnosed with each of the conditions by a doctor. Central Survey Unit (2007). Northern Ireland Health and Wellbeing Survey 2005/06. Northern Ireland Statistics and Research Agency: Belfast. 51

11 Figure 2.10a Prevalence of myocardial infarction by sex and country, latest available year, United Kingdom Prevalence (%) 4 3 England, 2006 Scotland, 2008 Wales, 2008 Northern Ireland, 2005/ Men Women Figure 2.10b Prevalence of stroke by sex and country, latest available year, United Kingdom 5 4 England, 2006 Scotland, 2008 Wales, 2008 Northern Ireland, 2005/06 Prevalence (%) Men Women 52

12 Figure 2.10c Prevalence of angina by sex and country, latest available year, United Kingdom England, 2006 Scotland, 2008 Wales, 2008 Northern Ireland, 2005/06 Prevalence (%) Men Women 53

13 Table 2.11 Prevalence of angina by sex and age, 2009, England, Scotland, Wales and Northern Ireland Prevalence (%) England Scotland Wales Northern Ireland United Kingdom All ages All ages Number of cases: 112,787 11,520 12,265 4,076 40,648 91,917 10,309 10,382 3, ,301 Estimates are based on records from a sample of general practices in each of the constituent countries of the United Kingdom. Estimates for all ages are age-standardised to the European Standard Population. General Practice Research Database (2010) Personal communication. This table is based on data from the General Practice Research Database, Copyright and database rights over the data belong to the Crown. The interpretation and conclusions contained in this report are those of the authors alone. Table 2.12 Prevalence of heart failure by sex and age, 2009, England, Scotland, Wales and Northern Ireland Prevalence rate (%) England Scotland Wales Northern Ireland United Kingdom All ages All ages Number of cases: 67,721 6,166 6,697 2,197 82,781 77,511 6,676 7,803 2,608 94, Estimates are based on records from a sample of general practices in each of the constituent countries of the United Kingdom. Estimates for all ages are age-standardised to the European Standard Population. General Practice Research Database (2010) Personal communication. This table is based on data from the General Practice Research Database, Copyright and database rights over the data belong to the Crown. The interpretation and conclusions contained in this report are those of the authors alone.

14 Table 2.13 Prevalence of coronary heart disease, stroke and hypertension by health authority, 2008/09, England, Scotland, Wales and Northern Ireland Registered GP CHD Stroke Hypertension patients Register Register Register count Prevalence count Prevalence count Prevalence United Kingdom 64,677,888 2,330, % 1,104, % 8,535, % England 54,310,660 1,886, % 901, % 7,132, % North East 2,661, , % 57, % 395, % North West 7,318, , % 135, % 987, % Yorkshire and the Humber 5,416, , % 102, % 721, % East Midlands 4,568, , % 78, % 623, % West Midlands 5,758, , % 98, % 812, % East of England 5,933, , % 95, % 793, % London 8,462, , % 88, % 915, % South East 4,525, , % 76, % 606, % South Central 4,271, , % 64, % 520, % South West 5,393, , % 104, % 756, % Scotland 5,367, , % 108, % 707, % Ayrshire & Arran 388,169 20, % 8, % 56, % Borders 115,908 5, % 2, % 16, % Dumfries & Galloway 155,343 8, % 3, % 23, % Fife 373,201 16, % 7, % 51, % Forth Valley 299,919 14, % 5, % 40, % Grampian 486,176 19, % 8, % 61, % Greater Glasgow & Clyde 1,306,295 56, % 26, % 163, % Highland 321,561 14, % 7, % 46, % Lanarkshire 590,103 27, % 11, % 77, % Lothian 845,379 30, % 15, % 100, % Orkney 20, % % 3, % Shetland 22, % % 3, % Tayside 415,376 19, % 9, % 58, % Western Isles 27,631 1, % % 5, % Wales 3,147, , % 63, % 469, % North Wales 699,536 30, % 14, % 106, % Mid and West Wales 1,063,104 46, % 23, % 162, % South East Wales 1,384,910 53, % 25, % 200, % Northern Ireland 1,852,027 75, % 31, % 225, % Eastern 726,617 31, % 13, % 89, % Northern 437,980 18, % 7, % 56, % Southern 372,607 13, % 5, % 42, % Western 314,823 11, % 4, % 36, % England Copyright Health and Social Care Information Centre Stroke refers to stroke and transient ischaemic attack. Prevalence (unadjusted) = (number on disease register / registered GP patients ) * 100%. Prevalence estimates for Shetland and Orkney are relatively unstable, due to their being based on a smaller number of patients. England Information Centre QOF achievement data 2008/09. Wales StatsWales. QOF 2008/09 achievement data. Scotland ISD Scotland. QOF achievement data 2008/09 Northern Ireland Department of Health, Social Services and Public Safety. QOF achievement data at health and social services board level. 55

15 Table 2.14 Prevalence of cardiovascular disease by age and sex, 1988 to 2008, Great Britain Prevalence (%) All ages Prevalence (%) All ages From 2000 data are weighted for non-response. See source for details. Office for National Statistics (2009). General Lifestyle Survey Results published online at Product.asp?vlnk=5756 (accessed June 2010). 56

16 Figure 2.14 Prevalence of cardiovascular disease by age, 1988 to 2008, Great Britain 45 Prevalence (%)