Epidemiology of IHD

Mortality rates

• Coronary heart disease (CHD) is the most common cause of death (and premature death) in the UK.
• 1 in 5 men and 1 in 6 women die from CHD.
• There are 101,000 deaths from CHD in the UK each year.
• Death rates from CHD have fallen by 46% for people under 65 years in the last 10 years. This fall is fastest in those aged 55 and over. It is largely due to a reduction in major risk factors (mostly smoking) and improvement in treatment and secondary prevention. The fall is not as high as that in some other countries such as Australia (48%) and Norway (54%).
• Death from CHD is more likely during winter.

Morbidity rates

• The average incidence of myocardial infarction is 600 per 100,000 in men aged 30-69 and 200 per 100,000 in women. The incidence increases with age.
• There are about 52,000 new cases of angina per year in all men living in the UK and about 43,000 new cases in women.
• About 4% of men and 2% of women in the UK have had a heart attack. Prevalence increases with age and is higher in men.
• About 8% of men and 5% of women aged 55 to 64 and 17% of men and 8% of women aged 65 to 74 have or have had angina.
• The prevalence of CHD is about 7.4% in men and 4.5% in women.
• The prevalence is higher in Scotland (4.6%) than in Wales (4.3%) or England (3.6%).
• The prevalence is higher in the North of England and Wales than in the South of England.
• The prevalence is higher in lower socio-economic groups.
• Of note, mortality from CHD is falling but morbidity appears to be rising.

• CHD is estimated to cost the UK economy over £7.9 billion a year (including direct health care costs and productivity losses).¹
• Among the more developed countries in Europe, only Ireland and Finland have a higher rate of CHD than the UK.¹

The aetiology of CHD is multifactorial. It is the result of interaction between genetic, lifestyle and environmental factors.

Age

• CHD increases with age. This is a non-modifiable risk factor.

Gender

• Traditionally, CHD has been considered a disease of men. However, CHD is the leading cause of death in both men and women.²
• It is responsible for a third of all deaths in women worldwide and half of all deaths in women over the age of 50 in developing countries.³

Social deprivation

• In England and Wales there is a positive correlation between deaths from circulatory diseases and levels of deprivation.
• There is a marked difference in prevalence of IHD between and within communities.¹
• Men and women living in the West of Scotland are nearly six times more likely to die prematurely from coronary heart disease than men and women living in the South West of England.¹
• Within London, people living in Tower Hamlets have a three times increased risk of dying prematurely from CHD than those in Kensington and Chelsea.¹
• The difference in CHD rates in different socio-economic groups is related to many factors including diet, smoking, exercise, alcohol.

Smoking

• Mortality from CHD is 60% higher in smokers.⁴
• Regular exposure to passive smoking increases CHD risk by 25%.^5,6,7
• About 1 in 8 deaths from cardiovascular disease (CVD) were attributable to smoking in 2000 in the UK.¹
• WHO research estimates that over 20% of CVD is due to smoking.⁸

Poor nutrition

• A World Health Organisation report in 2003 stated that a diet high in fat (particularly saturated fat), sodium and sugar and low in complex carbohydrates, fruit and vegetables increases the risk of cardiovascular disease.⁹
• COMA recommended in 1994 that the percentage food energy derived from fat should be 35%, with 11% from saturated fat.¹
• The Scientific Advisory Committee on Nutrition suggests that salt intake should be no more than 6g per day.¹
• The National Diet and Nutrition Survey in 2000/01 found that the total energy intake from fat was 36% in men and 35% in women with 13% from saturated fat. It also found that the average intake of fruit and vegetables was less than 3 portions per day compared to the recommended 5 portions. In the same survey salt intake was 11g per day for men and 8.1g for women.¹
• There are national, regional, socio-economic and ethnic differences in nutrition.
• Trans fatty acids reduce HDL and increase LDL-cholesterol and can increase coronary heart disease risk. A meta-analysis showed that a 2% increase in the energy intake from trans-fatty acids increased CHD incidence by 23%.¹⁰
• Eating oily fish rich in omega-3 fatty acids has been shown to reduce CHD mortality.¹¹
• Increased intake in dietary fibre also appears to reduce risk.

Infrequent exercise

• Physical activity reduces the risk of CHD.
• The 2002 World Health Report estimated that over 20% of CHD in developed countries was due to physical inactivity.⁸
• Recommended physical activity levels are 30 minutes of moderate physical activity on 5 or more days per week.
• In 2003, over one third of UK adults were inactive (exercised for less than one occasion of 30 minutes per week).¹

Alcohol

• 1 to 2 units of alcohol per day reduces the risk of CHD. Alcohol increases HDL cholesterol and reduces thrombotic risk. Higher levels of consumption increases risks from other causes.
• The World Health Report in 2002 estimated that 2% of CHD in men in developed countries is due to excessive alcohol consumption.⁸
• Men should drink no more than 3 to 4 units on any one day and women no more than 2 to 3 units.

Psychosocial wellbeing

• Work stress, lack of social support, depression, anxiety and personality (particularly hostility) can all increase CHD risk.¹

Blood pressure

• For adults aged 40 to 69 years, each 20 mmHg rise in usual systolic blood pressure or 10 mmHg rise in diastolic blood pressure doubles the risk of death from CHD.¹²
• The INTERHEART study showed that 22% of heart attacks in Western Europe were due to a history of high blood pressure and those with hypertension had almost twice the risk of a heart attack.¹³

Cholesterol

• CHD risk is related to cholesterol levels.
• The INTERHEART study suggested that 45% of heart attacks in Western Europe are due to abnormal blood lipids.¹³
• People with low levels of HDL-cholesterol have an increased risk of CHD and a worse prognosis after a myocardial infarction.¹
• In the UK, it is suggested that the target cholesterol is < 4 mmol/l for people with diabetes or established CVD or for people at high risk of developing CVD. People with HDL-cholesterol < 1 mmol/l should also be considered for treatment.¹⁴

Overweight and obesity

• Obesity is an independent risk factor for CHD. It is also a risk factor for hypertension, hyperlipidaemia, diabetes and impaired glucose tolerance.
• Central or abdominal obesity is most significant. Those with central obesity have over twice the risk of heart attack.¹³

Diabetes

• Men with Type 2 diabetes have a 2 to 4 times greater annual risk of CHD; women have a 3 to 5 times greater risk.¹⁵
• Over 4% of men and 3% of women in England have diagnosed diabetes.¹ The prevalence is increasing.

Ethnicity

• South Asians living in the UK (people from India, Pakistan, Bangladesh and Sri Lanka) have a higher premature death rate from CHD (46% higher for men; 51% higher for women).¹
• Hypotheses for this include migration, disadvantaged socioeconomic status, 'proatherogenic diet', lack of exercise, high levels of homocysteine and LP(a) lipoprotein, endothelial dysfunction and enhanced plaque and systemic inflammation.¹⁶
• The premature death rate from CHD in West Africans and people from the Caribbean is much lower (half the rate compared to the general population for men and two-thirds of the rate for women).¹

Family history

• First degree relatives of patients with premature myocardial infarction have double the risk themselves.¹⁷
• Premature coronary heart disease is that before 55 years in men and 60 years in women.
• More than one third of admissions for premature myocardial infarction could be prevented by screening and treating first degree relatives.¹⁷
• Genetic predisposition and shared lifestyle are likely to contribute.
• Several regions of the human genome have been shown to be associated with either CHD or hypertension.

Serum homocysteine

• It was previously thought that elevated levels of homocysteine is an independent risk factor for IHD, likely to due oxidative damage to endothelium, platelet activation and thrombus formation. The theory was that dietary supplementation with folic acid could reduce homocysteine levels and therefore CHD incidence.
• A meta-analysis in 2005 disputed this.¹⁸

• The target set in the 1999 White Paper 'Our Healthier Nation' was to reduce the death rate from CHD, stroke and related diseases in people under 75 years by at least 40% by 2010.
• The National Service Framework (NSF) for Coronary Heart Disease was set out to help achieve this.^19,20
• A recent summary of the NSF progress and impact has shown that this target was met 5 years ahead of schedule.²¹
• The same White Paper also set out the target to reduce inequalities in premature CHD death rates between deprived areas and the population as a whole by 40%.
• The recent NSF summary showed that there has been a 32% reduction in this gap so far.²¹