Most people are aware of the health risks associated with obesity – heart disease, diabetes, strokes, arthritis and certain forms of cancer. But a recent study from Sweden, suggests that being overweight or obese in middle-age may also significantly increase the risk of dementia.
The study recruited 8,534 participants from a nationwide twin registry in Sweden (the Swedish Twin Registry). The participants were twins, born in 1935 or earlier, and were aged over 65 years at the time of the current assessment (average 74 years). The study included both identical and non-identical pairs of twins.
The participants took part in a phone interview that screened for the most common diseases and which also included a brief assessment of their cognition (mental state). They were asked about their current height and weight, educational background, demographic factors, current health, past medical history and use of medication. They were also asked to provide an estimate of their weight during middle-age (on average 43-years of age).
The researchers found that, compared to people of normal weight people (at middle age), overweight people (at middle age) were 71% more likely to have any kind of dementia in their current older age. People who were obese during their middle age were almost four times more likely to have dementia of any type.
These findings are consistent with other studies. For example, in a 2005 study involving more than 10,000 men and women followed for over three decades, the US National Institutes of Health found that obese people in their 40s are 74% more likely to develop dementia compared to those of a normal weight.
As yet, it is unclear as to whether obesity increases the risk of dementia by a direct effect on the brain, or by its association with medical conditions such as diabetes and cardiovascular disease, that are also known to increase dementia. In the Swedish study, even allowing for diabetes and cardiovascular disease at mid-life and later did not alter the strength of the associations. So it could be that certain proteins produced by fat cells have a direct impact on brain tissue causing inflammation and shrinkage of brain cells.
Whatever the mechanisms, it now seems clear that the increasing burden of obesity, may well be matched by a rapid rise in rates of dementia in later life.
Dr David Ashton MD PhD
18th January 2013