Underweight people run ‘highest risk’ of dementia

A team of researchers at Oxon Epidemiology and the London School of Hygiene and Tropical Medicine have found that being overweight cuts the risk of dementia and that people who are underweight are at the ‘highest risk’ of developing the condition in their lifetime.

The analysis, published on The Lancet Diabetes & Endocrinology website is the largest and most precise investigation into the relationship, taking medical records from 1,958,191 people aged 55, on average, for up to two decades.

The researchers admit they were surprised by the findings, which run contrary to current health advice, while Dementia charities still advised not smoking, exercise and a balanced diet.

The research revealed that underweight people had a 39% greater risk of dementia compared with being a healthy weight, but those who were overweight had an 18% reduction in dementia - and the figure was 24% for the obese.

"Yes, it is a surprise," said lead researcher Dr Nawab Qizilbash speaking to the BBC News website: "The controversial side is the observation that overweight and obese people have a lower risk of dementia than people with a normal, healthy body mass index.

"That's contrary to most if not all studies that have been done, but if you collect them all together our study overwhelms them in terms of size and precision."

The BBC reports that any explanation for the protective effect is distinctly lacking. There are some ideas that vitamin D and E deficiencies contribute to dementia and they may be less common in those eating more.

Qizilbash said the findings were not an excuse to pile on the pounds or binge on Easter eggs.

"You can't walk away and think it's OK to be overweight or obese. Even if there is a protective effect, you may not live long enough to get the benefits," he said adding that heart disease, stroke, diabetes, some cancers and other diseases are all linked to a bigger waistline.

Dementia is one of the most pressing modern health issues with the number of patients globally expected to treble to 135 million by 2050.

There is no cure or treatment, and the mainstay of advice has been to reduce risk by maintaining a healthy lifestyle, although recent results might suggest this advice is misguided.