People who are severely obese in their 30s are three times as likely to develop dementia in old age as their peers, according to a UK study.
The study in the journal Postgraduate Medical Journal suggests that the later in life we become obese, the lower the increased risk of dementia.
Almost 66 million people around the globe are expected to have dementia by 2030, with the numbers predicted to top 115 million by 2050.
There is growing evidence that obesity is linked to dementia but the research indicates that risk may be heightened or lowered, depending on age.
Analysis revealed an incremental decrease in overall risk of hospital admission for dementia the older a person was when a diagnosis of obesity was first recorded, irrespective of gender.
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.
This is an observational study so no definitive conclusions can be drawn about cause and effect.
But the findings by researchers at the University of Oxford 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.
They venture that 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 arethemselves linked to a heightened risk of dementia.
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