Those whose cholesterol levels had increased since middle-age were, on average, 32 per cent less likely to suffer from dementia, Alzheimer's and memory loss, say researchers from the Icahn School of Medicine, who studied 1,897 people aged between 75 and 94 years.
The correlation between cholesterol levels and mental ability became most marked when the person reached the age of 85, and it continued to have a protective effect for a further nine years, the oldest age the study tracked.
Not surprisingly, those with the highest cholesterol levels weren't taking statin drugs, which lowers levels, the researchers noted.
The researchers said they were "perplexed" by the paradox—except there is no paradox. LDL cholesterol—the supposedly 'bad' type—protects the brain as we age, and the rising use of statins can, in part, explain the increase in rates of dementia and Alzheimer's.