Excess weight in your 50s increases risk of dementia, study finds
Middle-age spread raises the risk of dementia by up to a third, a University College London study has found.
A study of more than 1.3 million people found that those with a high body mass index in their 50s were much more likely to develop the neurological condition two decades later.
The research, published in the journal 'Alzheimer's and Dementia', found that being overweight leads to a reduced flow of blood to the brain.
Excess body fat is harmful to the cerebrovascular system, the vessels that carry blood to and from the brain.
Arteries supply oxygenated blood to the brain, boosting mental function.
"Reduced cerebral flow is obviously one possibility, but there are many other mechanisms, involving for example the quantity and secretory capacity of peripheral white adipose tissue as well as disturbed insulin regulation and its multiple effects on the central nervous system," Professor Mika Kivimaki, of UCL, said.
A Cambridge University study published last year found that being overweight in middle-age makes the brain age by 10 years.
The study, which scanned 473 brains, found changes in the brain structure of overweight people which are normally seen in those far older.
The volume of white matter - the tissue that connects areas of the brain and allows information to be communicated between regions - shrunk far more in those with a Body Mass Index above 25.
Human brains naturally shrink with age, but scientists are increasingly recognising that obesity - already linked to conditions such as diabetes, cancer and heart disease - may also affect the onset and progression of brain ageing.