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problems in the Middle-Eastern countries even more apparent, and 6 of the 10 countries with the highest diabetes prevalence were in this region. With standardised diabetes prevalences of 20% reported in the United Arab Emirates (10), and 11% in Egypt (17,18), the high rates of diabetes are being seen across the economic spectrum within this region.

Regional Prevalences of Diabetes

Europe

As in many regions of the world, the prevalence of diabetes varies considerably in Europe. The northern European countries are within the low to moderate range of diabetes prevalence. However, studies from both southern and eastern Europe have higher prevalences, with data from Spain indicating a prevalence of 10.3% in those aged 30-89 yr (19), and from Poland reporting a prevalence of over 15% (20). Ethnic groups originating outside Europe often differ significantly from Europids (people of white European origin) in their risk of diabetes. In the city of Coventry in England, the prevalence of type 2 diabetes was 3.2% and 4.7% respectively in Europid men and women, compared to 12.4% and 11.2% in Asian (predominantly from the Indian sub-continent) men and women (21). The higher prevalence of diabetes in the Asian than the Europid population was not owing to increased obesity, demonstrating, as in a number of other studies, that a lesser degree of excess adiposity is required in Asians than in Europids to precipitate diabetes.

Africa

Prevalence estimates for diabetes reported for a number of North African countries are in keeping with the high prevalences seen in the ethnically similar countries in other parts of the Middle East. For example, among a population-based sample in Algeria, aged 30-64 yr old, the prevalence of diabetes was 8.2% (22). In Egypt, the prevalence among adults aged 20 yr and older was 9.3% (17), and in Morocco, the prevalence was 6.6% among those aged 20 yr and older (23), and was twice as high in the urban population as in the rural population (9.0 vs 4.4%). This Moroccan study only used a fasting glucose to define diabetes, and so will have underestimated the prevalence that would have been found using an oral glucose tolerance test (OGTT), but nevertheless indicates the magnitude of the burden of diabetes faced by such populations.

Data from other parts of Africa show somewhat lower prevalences of diabetes, with figures of 6.4% for adults aged 25 yr and above in Ghana (24), and less than 1% in Cameroon (25), though more recent data from Cameroon have suggested rates standardised to the world population of 4% (26). Three studies of black South Africans reported prevalences of 4.5% to 8.0% (27-29), and data from the East African country of Tanzania indicate a diabetes prevalence of approx 3.5%(4).

One of the key factors in the measured prevalences of diabetes in Africa, as well as in other parts of the developing world, is the degree of urbanization. Those people living in rural settings, in which high levels of physical activity are part of daily life, have a much lower risk of diabetes than do their urban counterparts. As urbanization and its consequent changes in lifestyle increases in the coming years, the likelihood is that there will be a significant rise in diabetes prevalence.

Asia

The vast continent of Asia includes many different ethnic groups, as well as many different lifestyles, ranging from the traditional, rural lifestyles to westernized lifestyles in the some of the largest and most densely populated cities in the world. The high prevalence of diabetes in Middle-Eastern countries has already been described, and in some of these countries, it appears that the clash of a strong genetic propensity to diabetes with urbanization, wealth, and a sedentary lifestyle has produced an epidemic of diabetes, in which, for example, 1 in 5 adults in the United Arab Emirates has diabetes (10). In India, there is little doubt that there has been a rapidly rising prevalence of diabetes in the last 15 yr. Recent data from 6 of the largest Indian cities showed that 12.1% of adults aged 20 yr and older had diabetes (30), and there has been a continuing increase shown for Chennai from 1995 to 2004 (31). In addition to age and obesity being major risk factors for diabetes, higher income was also an important risk factor. Another Indian study showed that in some of the smaller cities (predominantly less than 1,000,000 inhabitants), the prevalence of diabetes among those aged 25 yr and older was lower at 5.9%, and was only 2.7% in rural populations (32). The very pronounced urban-rural and wealth gradient in the risk of diabetes in India once again demonstrates the importance of environmental factors. Because most of the Indian population is currently classified as rural, the potential for a further rise in the national prevalence of diabetes with increasing urbanization is clearly substantial.

In China, the prevalence of diabetes is lower than in India and the Middle East, but at 5.5% (33), is double that reported 10 yr ago (34). Higher prevalences reported in Chinese populations in Singapore, Hong Kong and Mauritius suggest that, as urbanization and westernization proceed, the prevalence in China will rise further. Although urbanization was once again an important risk factor in this study (33), underdiagnosis of diabetes was also identified as a problem. Many population-based studies have found that among all cases of diabetes, approximately half are previously undiagnosed, but in the Chinese study, this figure was 76%.

Perhaps the most concerning diabetes estimate to emerge from Asia is from Cambodia. King et al reported an unexpectedly high prevalence of 5% in a rural setting and 11% in an urban population (35), given the relative poverty and lack of westernization in this country.

Australasia/Pacific

Although Australia includes a wide range of ethnic groups, including Aboriginals and migrants from Europe, Asia and many other parts of the world, the large majority are from an Anglo-Celtic or other European background, and hence would be expected to have a similar prevalence of diabetes to that seen in Europe. The AusDiab study (36) is one of the few nationally representative studies in the world, and reported a prevalence of 7.4% among adults aged 25 yr and over in 1999-2000. Comparison with another Australian study from 1981 (37) not only shows that the prevalence of diabetes has risen, but that this is not simply a consequence of the aging of the population. The age-specific prevalence has also risen (Fig. 2): above the age of 35, the prevalence of diabetes is higher within each age group in 1999/2000 than it was in 1981. Figure 2 also demonstrates the strong relationship between age and diabetes, with a rapidly rising prevalence of diabetes seen with increasing age.

The Aboriginal population in Australia, though small, demonstrates up to 30% (38) prevalence of diabetes, one of the highest reported anywhere in the world. However, return to traditional lifestyles has been shown to rapidly reverse metabolic abnormalities, with fasting glucose falling from 210 to 120 mg/dL, and fasting insulin falling by 50%, when a group of Aborigines with diabetes returned to a hunter-gatherer lifestyle for 7 wk (39).

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