Early to mid-life obesity appears to be linked to a heightened risk of dementia in later life, according to a new observational study. People who are admitted to the hospital with obesity in their 30s have more than a 3-fold risk of developing dementia later in life. However, the risk of dementia is reduced in those admitted with obesity in their 80s or 90s.
“Obesity is associated with a risk of dementia in a way that appears to vary with age,” state University of Oxford researchers Clare J. Wotton and Michael J. Goldacre.
There is growing evidence that obesity is linked to dementia, but the research indicates that risk may be heightened or lowered, depending on age.
The Oxford researchers conducted a record linkage cohort study using national administrative statistical data on hospital care and mortality in England, 1999–2011. The records of those with obesity were then searched for any subsequent care for, or death from, dementia. During the study period, more than 450,000 of those admitted to the hospital had a diagnosis of obesity.
The analysis shows an incremental decrease in overall risk of hospital admission for dementia with increasing age of obesity diagnosis. For those aged 30-39, the relative risk of developing dementia was 3.5 times higher than in those of the same age who were not obese. For those in their 40s, the equivalent heightened risk was 70% more; for those in their 50s it was 50% more; and for those in their 60s it was 40% more.
Obese people in their 70s had no heightened or lowered risk of dementia, and those in their 80s were 22% less likely to develop dementia.
“An increased risk associated with mid-life obesity may be specific to vascular dementia,” the researchers noted. Those with obesity in their 30s were at greater risk for developing vascular dementia or Alzheimer disease. A diagnosis of obesity in the 40s to 60s was associated with an increased risk of vascular dementia, while the risk of Alzheimer disease was lower in those in whom obesity was diagnosed from their 60s onward.
A possible explanation for the particularly high risk found in early to mid-life may lie in the fact that heavier weight is associated with diabetes and cardiovascular risk factors, which have also been linked to a heightened risk of dementia.
The researchers note that the findings confirm smaller published studies showing an increased risk of dementia in young people who are obese, but a reduced risk in older obese people.
They suggest that if people can stave off significant weight gain until at least their 60s, or survive long enough with obesity, they may have a lower risk of developing dementia.
“While obesity at a younger age is associated with an increased risk of future dementia, obesity in people who have lived to about 60-80 years of age seems to be associated with a reduced risk,” they conclude.
The researchers published their results online on August 20, 2014, in Postgraduate Medicine Journal.