Half of all people of South Asian, African and African Caribbean descent will develop diabetes by age 80 according to a new study published today. The study is the first to reveal the full extent of ethnic differences in the risk of developing type 2 diabetes and also provides some answers as to the causes of the increased risk.
The findings come from the Southall and Brent REvisited (SABRE) study, a large-scale population based study funded by the Wellcome Trust and British Heart Foundation which has followed nearly 5000 middle-aged Londoners of European, South Asian, African and African Caribbean descent for over 20 years.
Type 2 diabetes is a long term condition that affects approximately 2.9 million people in the UK. In total, an estimated -11.9billion is spent each year on treating type 2 diabetes and its complications. Early diagnosis and careful management are vital in order to prevent complications such as heart attack, stroke and kidney disease.
It has been known for some time that people of South Asian, African and African Caribbean descent are at increased risk of developing diabetes in mid-life, but it is not known why this is or whether this extra risk continues as people get older. By tracking the development of diabetes in the SABRE cohort, researchers led by Nish Chaturvedi at Imperial College London have revealed the extent of the problem in the UK and offer some explanations as to why these differences arise.
The study reveals that by age 80, twice as many British South Asian, African and African Caribbean men and women had developed diabetes compared with Europeans of the same age. Approximately half of all South Asians, Africans and African Caribbeans in the UK will develop the disease by age 80 compared with only one in five of European descent.
The study looked at individuals who did not already have type 2 diabetes at the start of the study, which began following participants aged 40 to 69 from 1988 onwards, and recorded those that developed the disease. The team found that while African, African Caribbeans and Europeans tend to be diagnosed at around the same age, 66-67 years, South Asian men were 5 years younger on average when diabetes was diagnosed, meaning that they are at even greater risk of complications.
In order to understand the causes of this increased diabetes risk, the researchers looked at a number of risk factors across the different ethnic groups.
Family history of diabetes is known to be an important risk factor for all ethnic groups. However, even though over half of South Asian, African and African Caribbean men and one third of women had a family history of diabetes, this did not explain the extra risk over their European counterparts.
It is known that the onset of type 2 diabetes is frequently preceded by an increase in insulin resistance, where the body becomes insensitive to the effects of insulin on glucose metabolism, resulting in high circulating glucose. Weight gain and obesity are known factors that can underlie increases in insulin resistance.
The team found that carrying fat around the trunk or middle of the body in mid-life together with increased resistance to the effects of insulin explained why South Asian, African and African Caribbean women are more at risk of developing diabetes than British European women. However, this explained only part of the increased risk in South Asian, African and African Caribbean men, suggesting that other factors that are as yet unknown may also play a part.
The findings are published today in the journal Diabetes Care.