Can physical fitness protect against dementia?

That's the possible conclusion from Swedish study published in Neurology in March 2018.

The health of 191 women was tracked over 44 years, from middle age to old age. What the study found was that the women with high physical fitness in middle age were nearly 90 percent less likely to develop dementia decades later, compared to women who were moderately fit. And when the highly fit women did develop dementia, they developed the disease an average of 11 years later than women who were moderately fit, or at age 90 instead of age 79.

The researchers caution that this shows an assocation between physical fitness and reduced risk of dementia rather than cause and effect - and accept that this was small scale study in one country, meaning more research is needed. However, these initial results are promising. 

It fits with other research we have seen which suggests that both physical and mental activity can prevent, or at least delay, the onset of dementia.