Researchers have linked obesity early to mid-life to an increased risk of developing dementia in later life.
An observational study published in the Postgraduate Medical Journal found the risk of dementia triples for those with severe obesity in their 30s.
Using anonymised hospital record data for England from 1999-2011, the researchers looked at records on obesity and looked for people who had been treated for, or who had died from, dementia.
There were 451,323 people admitted to hospital who had been diagnosed with obesity. The researchers, from the University of Oxford, found that the risk of demential fell depending on how old the patient was when first diagnosed with dementia.
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 fell to 70% more; for those in their 50s to 50% more; and for those in their 60s to 40% more.
People in their 70s with obesity were neither at heightened or lowered risk of developing dementia, while those in their 80s were 22% less likely to develop the disease, the findings indicated.
Recent estimates show that almost 66 million people across the world will have dementia by 2030, with the numbers predicted to reach 115 million by 2050.
The findings confirm smaller published studies from elsewhere which report an increased risk of dementia in young people who are obese, but a reduced risk in older obese people, say the researchers.
They suggest 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 are themselves linked to a heightened risk of dementia.
And it would seem 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, they suggest.
“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.