Department of Community Health Sciences, St George's Hospital Medical School, Cranmer Terrace, London SW17 0RE, UK. E-mail: f.cappuccio{at}sghms.ac.uk
The study of change in patterns of health and disease across populations has been of interest since Thomas Malthus in 1798 argued that population growth will always tend to outrun the food supply and that betterment of the lot of mankind is impossible without stern limits on reproduction.1 Since then, the theories on the health of populations in transition have developed2 with the groundbreaking contribution given to public health by Abdel Omran.3 In his essay of 1971 Omran conceptualizes with five propositions the theory of epidemiological transition in which degenerative and man-made diseases displace pandemics of infection as the primary causes of morbidity and mortality. The determinants of this transition, in his view, are ecobiological (interaction between biology and environment), socioeconomic, psychological, and medical (biotechnology and public health). Furthermore, Omran distinguishes between the Classical transition (gradual and progressive from high mortality and high fertility to low mortality and low fertility) seen in England & Wales in the 19th century, the Accelerated transition (faster decline in mortality rate) seen in Japan in the early 20th century, and the Contemporary transition (slow and unsteady decline in mortality, but high fertility rates, thus rapid population growth) currently seen in developing countries. In societies around the world we now observe two main distinct phenomena: first, a rapidly growing movement of populations between locations where there are large differences in health indicators or where there are differences in the nature and practice of health care. Migration and mobility of populations are responsible for health differentials between origin and destination.4 Second, whilst the transition in the now developed countries was predominantly socially determined, the transition in the now developing countries is significantly influenced by medical technology. Indeed, with the control of the traditional infectious diseases (e.g. diarrhoea, malaria, and tuberculosis) and the decline in infant mortality rates, chronic diseases are becoming more prevalent. Ischaemic heart disease and stroke are now the most common causes of death in the world. Seventy per cent of these deaths occur in developing countries.5,6 Even considering the impact of the HIV/AIDS epidemic, they will remain the most common causes of morbidity, disability, and death in developing countries in 2020.5,6
An intriguing aspect of the epidemiology of vascular disease around the world is the consistent report that stroke is an important cause of morbidity, disability, and death in adults of black African origin, whether living in Africa, the Caribbean, US, or the UK.7 After studying trends in stroke mortality in the US among African Americans,8 Gillum has suggested six stages of the epidemiological evolution of patterns of cardiovascular disease among black people of sub-Saharan African origin (Figure 1). 9 The evolution is characterized by advancing acculturation, urbanization, and affluence with a progressive increase in salt intake, smoking habit, and saturated fat intake. The earlier stages (from 2 to 4) see the appearance of hypertension (and associated stroke) as the predominant form of cardiovascular disease whilst atherosclerosis (and associated ischaemic heart disease) is predominant in the later stages (4 and 5). In stage 6 Gillum then postulates a decline in morbidity and mortality from vascular disease attributable to better prevention and management. Interestingly, he explains the low mortality rates in Caribbean-born African Americans under the age of 65 by the selective migration of the better-educated and more affluent. The transition of many from the original stage 3 (moderate affluence, fat intake, and smoking, and high salt intake and hypertension) to stage 6 (high affluence, moderate fat intake, smoking, and salt intake, and controlled hypertension and atherosclerosis). This contrasts with the high mortality rates common to older Caribbean-born African Americans as well as US-born African Americans. This could be attributed to migration in an earlier era, when access to the educational and employment opportunities was barred to most black people in the US, thus forcing them into stage 5 (moderate affluence, high fat intake, smoking, and salt intake, and high hypertension and atherosclerosis).9
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Notwithstanding the limitations, the present study highlights an important area of research currently grossly neglected and under funded in the UK. With the growing importance of ethnic background for the understanding of disease processes, tailoring management strategies,13 and improving health care services, there is a need for prospective data in ethnic minorities in the UK. In the meantime, an attempt should be made to best use available data on ethnic minority groups nationally.
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