The substantial declines in coronary and stroke death rates for those born in England and Wales are similar to those in other Western European countries and are consistent with favourable long-term changes in population risk factors (smoking, cholesterol, blood pressure) and in treatment.8 9
Few data on risk factor trends for migrant groups are available, but the results here correspond with a gradual convergence of risk for some groups towards that of England and Wales. The relative impact of risk factors such as obesity and diabetes may differ across migrant groups but generally smaller declines compared with those born in England and Wales suggest a lag in behaviour modification or differential access to quality care, or both.
The Health Survey for England10
is the only national data source of risk factor exposures for ethnic groups. Trends for smoking provide some evidence of an emergent harmful exposure influencing cardiovascular risk in both men and women from the Caribbean and men of Pakistani and Bangladeshi origin. In 2004 smoking prevalence among Black Caribbean men and women was similar to that of the general population, while for Pakistani and Bangladeshi men it was higher. The proportion of ex-regular smokers in these groups was lower and of those who never smoked was higher. Local studies suggest that the prevalence of smoking in Caribbeans was previously low,5 11
so a rise in smoking is plausible. A rise can also be expected for South Asians as findings from the Stockport Stroke Risk Factor Screening Programme showed an increase in smoking prevalence in South Asians between 1988 and 1999.12
Heterogeneity of risk in South Asians is known.13 14
Our analyses suggest that the lack of decline observed for South Asian migrants in the earlier work2
was largely due to the trends for Pakistani and Bangladeshi migrants. There are no data on long-term trends in risk factors for the individual South Asian groups but the data from the Health Survey for England10
suggest that trends in mortality may continue to be relatively more adverse for Bangladeshis and Pakistanis than Indians. Between 1999 and 2004, the prevalence of cardiovascular disease in Pakistanis doubled, and among women aged 55 years and older, the prevalence of diabetes was more than fivefold that of all women and increased by 16% (compared with 2% for all women). The prevalence of overweight including obesity in Bangladeshis, though lower than for the general population, increased between 1999 and 2004 by 8% for men and 14% for women (compared with 4% for all men and 3% for all women) and the prevalence of diabetes was highest in Bangladeshi men, fourfold that of men in general, in both years.
There was a large rise in Bangladeshi migrants (70% for men) between the 1991 and 2001 censuses compared with Pakistani (38% for men, 47% for women) or Indian (6% for men, 12% for women) migrants, suggesting that exposures in home countries might be relatively more important for Bangladeshis. In the INTERHEART study of South Asians in South Asian countries, Bangladeshis had the highest prevalence of most risk factors compared with other South Asians.6
The size of the Caribbean population reduced for men and changed little for women, suggesting less influx of new migrants so that acculturation to UK lifestyles may have a role. Other work signals that a change in coronary risk among Caribbeans can be expected, with a shift away from traditional diets with high fresh fruit and vegetable content15
and a lowering of the level of protective high-density cholesterol.16
International comparative data also provide supporting evidence for a faster transition in coronary risk for Caribbeans than West Africans. The prevalence of diabetes17
in populations of African origin living in the Caribbean is intermediate between those of Africans in Africa and in Britain.
The impact of differential access to health care on ethnic differences in cardiovascular mortality is unclear. South Asians are more likely to seek care but the quality of medical management has been questioned.19
South Asians are less likely than White British to present with classic symptoms of myocardial infarction, and some argue that this makes diagnosis difficult and possibly delays essential treatment. Bangladeshis and Pakistanis appear to fare worse than Indians as they are less likely to have invasive management of coronary disease.20 21
Declining case fatality rates among South Asians, however, for acute myocardial infarction between 1998 and 2002 and reduction in infarct severity suggest improvement in survival and correspond with the data reported for the second decade.22
In the Health Survey for England 2004,10
the prevalence of high blood pressure was greater than average only among Black Caribbean, Black African and Bangladeshi women, suggesting that the consistent excess stroke mortality for most groups is linked to differences in access to healthcare. The evidence suggests that although detection and control of hypertension may have improved, ethnic differences remain.10 11
The results for Southern/Eastern European and French migrants are partially consistent with rates in home countries, suggesting some retention of risk. Coronary mortality is lower in Italy, France and Spain than the United Kingdom and higher (though declining) in Poland (since the late 1990s) and Hungary (since the late 1980s).23
Stroke mortality among men in Poland and Hungary is more than twice that of the United Kingdom. The cause of low coronary mortality in Southern European countries and France continues to be debated, but is generally thought to be linked to high intake of monosaturated fats and antioxidants in Southern Europe.24
Whereas men from Italy or Spain retained lower coronary mortality than men born in England and Wales, the rates for men from France were not significantly different, which raises the question of whether retention of traditional behavioural practices differs across the groups. Higher cardiovascular mortality in Eastern Europe has been linked to higher levels of smoking, alcohol consumption and saturated fat intake.25
Greater socioeconomic disadvantage among minorities may contribute to smaller declines in mortality. Persisting disadvantage is more common among South Asian and Caribbean migrants, and downward mobility is associated with more ill health among Caribbeans.26
Research on the impact of disadvantage on ethnic differences in cardiovascular health is limited13
(and non-existent for Southern or Eastern European migrants). The evidence suggests that higher disadvantage does not fully explain the patterns of excess mortality observed.4
Our results are subject to the usual limitations of cross-sectional data—notably, misclassification of country of birth between the census and death certificates, and selection bias (health status on migration). This is most pertinent for older South Asians. Pakistanis and Bangladeshis born before the formation of Pakistan (1947) and Bangladesh (1971) may have recorded India as country of birth in the census but relatives may have reported Pakistan or Bangladesh at death. Temporal trends might be influenced by cohort trends—age at entry to the UK and duration of exposure to the UK environment all being potential confounders.27
Stratification by age provides some clues of cohort effects if we assume that older migrants have longer duration of residence. These data were not included owing to space restrictions. The trends were largely consistent at ages 45–59 and 60–69 years. Migration flows may also affect cross-sectional analyses of mortality trends. New migrants may have increased mortality risks owing to low uptake of healthcare, and people at high cardiovascular risk might have migrated.
Reliable national trend data from West Africa and the Indian subcontinent are lacking, but local studies suggest that cardiovascular risk, though changing, remains lower in comparison with British data. Most West Africans in Britain are from Ghana and Nigeria where hypertension prevalence is lower than for Africans in the UK.28 29
The Caribbean, Polish and Hungarian populations are least likely to be affected by an influx of new migrants. Ending right of entry from British colonies to the UK after the 1962, the Commonwealth Act largely stemmed the Caribbean inflow. Before 2004, Hungarian and Polish migrants arrived mainly after the second world war. The longstanding debate on whether the high mortality associated with Scottish and Irish migrants is related to inflows of ill-fit individuals (linked to ease of migration) may be relevant, though the high mortality of second and third generations of Irish born in the UK30
challenges this as the sole explanation. ICD10 assigned more deaths to stroke than ICD9, but this is unlikely to affect differences in trends by country of birth groupings as this bias should affect all groups equally.