Middle-age spread may protect against dementia

Middle-age spread may protect against dementia

The middle-aged spread may protect against dementia, scientists have suggested, after the largest ever study found that obese people have the lowest risk of developing the devastating condition.

In findings which contradict current medical advice to exercise regularly and eat well, obese people with dangerously high BMIs (Body Mass Index) were 30 per cent less likely to be diagnosed with the disorder.

It means that a 5ft 10 man who weighed 20 stone in his 50s would be a third less likely to develop dementia that someone who weighed just 10 stone.

Scientists at the London School of Hygiene and Tropical Medicine said they were baffled by the results as previous studies have shown that being overweight raises the risk.

“Our results suggest that doctors, public health scientists, and policy makers need to re-think how to best identify who is at high risk of dementia,” said Professor Stuart Pocock from the Medical Statistics Unit at the London School of Hygiene & Tropical Medicine.

“It opens up an intriguing new avenue in the search for protective factors for dementia. If we can understand why people with a high BMI have a reduced risk of dementia, it’s possible that further down the line, researchers might be able to use these insights to develop new treatments.”

Researchers analysed the medical records of nearly two million people with an average age of 55 years and an average BMI of 26.5.

Nearly 50,000 people developed dementia during the nine year follow up period, yet those with the highest BMIs were the least likely to suffer.

Instead, underweight people had a 30 per cent greater risk of being diagnosed with the condition than normal weight people, and the chances of developing the disorder gradually declined as participants gained more weight.

Previous studies have suggested that gaining weight in older age can help protect against osteoporosis, but it is the first study to find a beneficial impact for dementia.

However, health experts and warned that misdiagnosis may be behind the unexpected findings.

“Is it time to slump on the sofa, pile into the burgers and slurp the lager? Probably not just yet,” said Tom Dening, Professor of Dementia Research a the University of Nottingham.

“The ascertainment of dementia is based on a GP diagnosis of dementia. It is plausible that faced with a grossly obese patient, the average GP may have concentrated on the obvious medical risks and paid less attention to the cognitive issues than they might have done with a comparable patient of normal weight.”

There are around 850,000 people currently suffering from dementia in Britain and the figure is expected to rise to one million by 2025. One in six people aged 80 and over have dementia.

Around 60,000 deaths a year are directly attributable to dementia and the Alzheimer’s Society has calculated that delaying the onset of dementia by five years would reduce deaths directly attributable to dementia by 30,000 a year.

Charities warned that a healthy lifestyle was still the best way to prevent against disease in old age.

Dr Doug Brown, Director of Research and Development at Alzheimer’s Society, said: “While the evidence on body weight and dementia is unclear, we know that people can make positive lifestyle choices to keep their brains healthy by taking regular exercise, not smoking and following a healthy balanced diet.”

Dr Liz Coulthard, Consultant Senior Lecturer in Dementia Neurology, University of Bristol, added: “We do know that obesity carries many other risks including high blood pressure, heart disease, diabetes and increased rates of some types of cancer. So maintaining a healthy weight is recommended.”

The research was published in the journal The Lancet Diabetes and Endocrinology.

By Sarah Knapton,

The Telegraph, Friday 10 April 2015

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