In the United States (US), recent predictions, which account for trends in risk factors such as obesity, the natural history of diabetes and the effects of treatments, suggest that the number of people with diagnosed and undiagnosed diabetes will double in the next 25 years from 23.7 million in 2009 to 44.1 million in 2034 (Huang et al., 2009). Furthermore, the researchers predict that even if the prevalence of obesity remains stable, diabetes spending over the same period will nearly triple to US$336 billion.
Factors driving the type 2 diabetes epidemic
Age
The prevalence of type 2 diabetes increases with age and with more people living well into old age the likelihood of developing the disease is increased. However, increases in prevalence have been observed in younger age groups in association with the rising prevalence of childhood obesity and physical inactivity (Ehtisham, Barrett and Shaw, 2000; Fagot-Campagna, 2000). This is a worrying finding given that the risk of complications increases with duration of disease.
Table 1.2 Prevalence of obesity in people registered in UK general practice
Source: Diabetes UK (2009). Reproduced with permission.
Figure 1.1 The growing epidemic of type 2 diabetes in relation to obesity (Mokdad et al., 2000). Data from Diabetes Care 2000; 23:1278–1283, Copyright 2000 American Diabetes Association.
Overweight and obesity
More and more of the world’s population is being exposed to the dietary habits and sedentary lifestyles of the developed nations. The increase in calorie intake, mainly derived from carbohydrates and animal fat, with a decrease in physical activity, has led to excessive obesity and increasing resistance to insulin action. Type 2 diabetes is strongly associated with overweight and obesity (Figure 1.1) (Mokdad et al., 2000), and a high proportion of people with type 2 diabetes are overweight or obese at the time of diagnosis, which may reach up to 80% in some populations (Hedley et al., 2004).
In the UK, rates of obesity have dramatically increased in the past two decades. The ongoing Health Survey for England highlights the increasing trend. In 1993, 13% of men and 16% of women were estimated to be obese (body mass index (BMI) >30 kg/m2) (DoH, 1994). Just over a decade later the proportion of men and women classed as obese had increased to 24% for both sexes (DoH, 2004). The Foresight report ‘Tackling Obesities: Future Choices’, which was commissioned by the UK Government, has estimated that if no action is taken, 60% of men, 50% of women and 25% of under-20 year olds will be obese by 2050 based on current trends (Foresight, 2007).
Socioeconomic class
The prevalence of diabetes appears to be higher amongst low socioeconomic groups, with a 36% higher prevalence noted amongst men living in the most deprived areas of England and Wales compared with those living in the most affluent areas. For women the prevalence amongst those living in the most deprived areas is 80% higher than amongst those living in the least deprived parts. Interestingly, the reverse situation is found in developing countries (Mohan et al., 2001).The tendency for the increased prevalence of type 2 diabetes to be concentrated in lower socioeconomic groups in developed countries and higher socioeconomic groups in developing countries probably reflects the adoption of a healthier lifestyle by better educated people in developed countries, while it is generally the affluent in developing countries who enjoy a high calorie intake and low level of physical activity.
Ethnicity
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