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Early obesity raises later risk of dementia

Mid-life obese people three times more likely to develop dementia

Adrian O'Dowd

Thursday, 21 August 2014

People who are obese in their early middle age are as much as three times more likely to develop dementia when they get older, concludes a study* published online today in Postgraduate Medical Journal.

UK researchers found that early to mid-life obesity had an association with dementia in later life, but the age at which a person becomes obese is a key factor, with an apparent tripling in risk for people in their 30s.

It is estimated that almost 66 million people globally will have dementia by 2030, with numbers predicted to rise to 115 million by 2050.

There is growing evidence that obesity is linked to dementia, but this new research suggests the risk may be heightened or lowered, depending on a person’s age.

No study so far has looked at the age related effect of obesity on dementia risk across the whole age range in the population of one country.

Researchers, therefore, focused on this aspect using anonymised data from hospital records for the whole of England for the period 1999-2011.

During the study period, 451,232 of those people admitted to hospital in England were diagnosed with obesity, 43% of whom were men.

Data in which obesity had been recorded was searched for any subsequent care for, or death from, dementia.

The researchers, led by Professor Michael Goldacre, from the Nuffield Department of Population Health, University of Oxford, found that the older a person was when they were diagnosed as obese, the less the overall risk of hospital admission for dementia, irrespective of gender.

For people 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 higher or lower risk of developing dementia, while those in their 80s were 22% less likely to develop the disease.

Further analysis showed there were some age differences between the risk of developing vascular dementia or Alzheimer’s disease, with those in their 30s at greater risk of both.

The authors stressed that this was an observational study, so no definitive conclusions could be drawn about cause and effect.

Nevertheless, they said their findings confirmed smaller studies from elsewhere which reported an increased risk of dementia in young people who were obese.

One possible explanation for the particularly high risk found in early to mid-life could 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.

They concluded: “Obesity is associated with a risk of dementia in a way that appears to vary with age. Investigation of the mechanisms mediating this association might give insights into the biology of both conditions.”

Dr Clare Walton, research communications manager at Alzheimer's Society, said: “Given the growing body of evidence that being overweight in mid-life rather than in later years seems to be the bigger risk factor for dementia, it is never too early to start making healthy lifestyle choices.”

* Goldacre M J, et al. Age at obesity and association with subsequent dementia: record linkage study. Postgrad Med J doi:10.1136/postgradmedj-2014-132571

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