Business Insider:

A study published this week in the journal Neurology suggested that women who were physically fit in middle age were roughly 88% less likely to develop dementia (defined as a decline in memory severe enough to interfere with daily life) than their peers who were only moderately fit.

Neuroscientists from the University of Gothenburg in Sweden studied 191 women whose average age was 50 for 44 years. First, they assessed their cardiovascular health using a cycling test and grouped them into three categories: fit, moderately fit, or unfit.

Over the next four decades, the researchers regularly screened the women for dementia. In that time, 32% of the unfit women were diagnosed with the condition; a quarter of the moderately fit women did. But only 5% of the fit women developed dementia.