Diseases and Different Ethnic Groups

The UK boasts a culturally diverse population with ethnic minorities accounting for almost 8% of the population in the 2001 census.¹ This represented an increase in the percentage of ethnic members of the population by approximately 50% in the decade spanning 1991-2001. The largest ethnic minority group was Indians, followed by Pakistanis, mixed ethnic backgrounds, Black Caribbeans, Black Africans and Bangladeshis.²

It is becoming increasingly apparent that each population group, either that determined by religion or ethnicity, have differences in terms of illness behaviour, seeking assistance with health matters and beliefs about illness. Some of these processes are determined by culture and more work is required to understand these reasons.

Nevertheless, it has become apparent that some diseases are more prevalent in certain ethnic groups. This is especially so for cardiovascular disease which is more prevalent in men from the Indian subcontinent. This has sparked a lot of interest and programmes to increase the detection of cardiovascular disease and its risk factors in ethnic groups are underway. There is also a deficit of ethnic minority participants in research trials, meaning that results may not necessarily correlate to patients from ethnic groups.

Cardiovascular related illnesses are still the largest cause of death in the United Kingdom, a fact which also applies to ethnic minority groups. Unsurprisingly, therefore most of the surveys have focussed on issues such as hypertension, diabetes mellitus and coronary heart disease. This article will focus on the results of two health surveys on ethnic minority groups in England.

Why these differences in predilection for illnesses exists across ethnic groups is unknown. Research to try and tease out the reasons are underway. But similar to clinical trials, a lot of this research has been performed in the United States and at present there are no cohort studies in the UK that include enough ethnic minority patients.³

In 1999⁴ and again in 2004, the Health Survey for England performed surveys on ethnic minority groups. Participants were randomly chosen and then visited by a researcher who obtained survey results. It included adults and children and various parameters were discussed. Following this a nurse visited some of the participants and undertook various tasks e.g. venepuncture, urinalysis etc.

Presence of cardiovascular disease in various ethnic groups

Presence of IHD and stroke is higher in men than women (as in the general population). There was an increase in the prevalence of CVD in all ethnic minorities but more worryingly the increase was particularly high in Pakistani men when the two surveys were compared.

According to the British Heart Foundation (BHF) South Asian men have an age standardised mortality rate from coronary heart disease that is about 40% higher than the whole population, and for women the figure is 51%.⁵ Again this was particularly noted in Pakistani men. The JBS2 guideline suggests when calculating the cardiovascular risk from the standard charts, users should multiply the calculated CVD risk by a factor of 1.5.⁶ However South Asians form a heterogeneous group as we shall see.

Presence of stroke in various ethnic groups

Black Caribbean men have a much higher prevalence of stroke - the risk is almost two thirds higher than the general population. Indian men also have a higher risk of stroke (relative risk 1.42).⁴ However, high rates of stroke were also seen in Bangladeshi women, Pakistani women and Irish men.

Furthermore, research from the US suggests that ethnic minority patients have more severe strokes and may do less well in rehabilitation.⁷

Interestingly the prevalence of angina and stroke were lower in both Chinese men and women, especially in the latter group.

There have been various theories as to the observed difference of cardiovascular disease in ethnic minorities. Possibilities include genetic variation and dietary influence. It is suggested that the risk factor profile is different in terms of intensity and prevalence. Let us explore some of these risk factors.

Diabetes mellitus

The 1999 and 2004 surveys both reported that the prevalence of diabetes is greater in men than women. The observed prevalence was markedly higher in Bangladeshi, Pakistani, Indian and Black Caribbean patients.⁴ For the Bangladeshi and Pakistani population this represents an almost 5 times higher prevalence than the general population. There were no significant changes between the prevalence rates when the two surveys were compared.

The prevalence of diabetes mellitus in Black Caribbean men was also similar to Indians. However, Black Caribbean women were noted to have the highest prevalence of diabetes mellitus amongst all women.

Hypertension

In the Health Survey for England 2001, the prevalence of hypertension was reported as over 25% in those over 40 years of age and nearly 50% in those aged 80 or over in the general population.⁸ Hypertension is more frequently encountered in ethnic minorities - although differences do not reach statistical significance.⁹ The average blood pressure is different in the differing ethnic groups. Another difference is the development and presence of target organ damage, for example, Black Caribbean patients have an increased prevalence of left ventricular hypertrophy (a predictor of mortality and morbidity independent of other risk factors).⁸

Hyperlipidaemia

There is no clear evidence that a difference in lipid levels exists between ethnic minorities.¹⁰ Despite this plasma lipid concentrations are greater in patients of South Asian descent (i.e. from the Indian subcontinent and East Africa - note that the BHF define South Asians as only from Indian countries).⁵ This may explain the differences in prevalence of cardiovascular disease seen between them and the Black Caribbean population.

Black Caribbean populations appear to have higher HDL fractions and lower triglycerides, where as Pakistani and Bangladeshi men are more likely to have low HDL levels. It is postulated that these changes probably represent genetic variations e.g. polymorphism of hepatic lipase genes.¹¹

Obesity

In the 1999 UK health survey obesity and raised waist-hip ratio was higher in those with cardiovascular disease and more so in Indian and Bangladeshi women.⁴

Smoking

Smoking levels in men of ethnic minorities is similar to the general population with a reduction in smoking rates since 1999. The use of chewing tobacco is higher in people of Bangladeshi background, but the rates appear to have decreased in the 2004 survey.

Other theories

• The pattern of atherosclerosis is thought to be different in African American and Caucasian patients - but this remains inconclusive. Levels of C-reactive protein (CRP) , an inflammatory marker, appear to be higher in ethnic groups and has been independently associated with cardiovascular disease - although the part it plays in the pathophysiology of atherosclerosis is still poorly understood.¹⁰ Despite this the 2004 survey did not report any differences in CRP in ethnic minorities compared to the general population.
• Another theory is that genetic differences resulting in changes in the bioavailability of nitric oxide, a potent vasodilator may be involved.¹²
• The most likely cause for the observed disparity in cardiovascular disease between ethnic groups probably relates to greater risk factor clustering - leading to a metabolic syndrome characterised by dyslipidaemia, obesity and hypertension.^10,13 This is supported by studies that have shown higher fasting insulin levels in Asian Indians in the United States when compared to Caucasians of a similar age and body mass index. This supports the presence of impaired insulin metabolism and use.
• The BHF states that the increased rate of cardiovascular disease in South Asians is probably due to the following: excess exposure to risk factors (e.g. environmental such as urban lifestyle), greater susceptibility, presence of a certain risk factor not yet determined and due to the fact there are fewer competing causes of death in this group e.g. cancer.⁵
• However, it has been argued that the observed differences actually relate to the fact that ethnic minorities are under investigated and under treated.^10,14

The Framingham study has provided us with valuable insights into the risk factors for cardiovascular disease and the time course of disease. This provided the Framingham risk function to determine the cardiovascular risk in a patient based on their risk factors. However, the cohort of patients has been mainly Caucasian making it difficult to correlate to ethnic minority groups,¹⁵ JBS guidelines suggests multiplying calculated risk by 1.5.⁶

Recently a risk calculator for determining the 10 year risk of coronary heart disease and cardiovascular disease for ethnic minorities has been developed and is based on the Framingham study.^3,16

• In the first instance this should be the same as your management of all patients.
• However, when considering the risk of a patient from a cardiovascular view point we need to take in to account their ethnicity - this includes cultural differences.
• BHF recommend that practices keep a register with ethnic codes and diseases.
• All patients should have their blood pressure, weight and height checked - these are easy to perform and non-invasive.
• Patients with a strong family history of diabetes, hypertension and hyperlipidaemia should have these parameters regularly checked e.g. annually.
• Have a high index of suspicion for the presence of multiple risk factors and use the risk calculator to determine the patients risk.
• Lifestyle modifications must be reinforced whenever possible and even if risk is low e.g. weight reduction, salt reduction, healthy low-fat diet and increased exercise.
• The above measures may require dedicated services available in the patients language e.g. gujarati smoking cessation service.
• Hypertension, diabetes mellitus and hyperlipidaemia should be aggressively treated and patients should be educated e.g. community ethnic diabetes mellitus meetings with professionals and patients.

• The 2004 survey also reported on self-reported health, longstanding illness and social support.
• Bangladeshi and Pakistani men and also Black Caribbean women are more likely to report bad or very bad health. The cause of this is unclear.
• Pakistani women and Bangladeshi men were more likely to report the presence of a longstanding illness which limited them on a daily basis. Furthermore, the figures had increased in Pakistani women by almost 10% when compared to the results of the 1999 survey.
• Of more concern, all ethnic minorities reported a severe lack of support, especially people of Pakistani and Bangladeshi origin.

Other areas of variation in illness/disease in ethnic minorities:
Perinatal mortality
Mental health