Brisk walking for two hours a week may help boost brainpower in women at risk of dementia, say researchers.

A six-month study in women with early memory problems found aerobic activity increased the size of the hippocampus - an area of the brain involved in learning and memory, reports The Daily Mail.

Canadian researchers claim it's never too late to undertake regular physical activity based on increasing evidence that it promotes brain health.

They investigated the effect of different types of exercise on the size of the hippocampus because it is very sensitive to the effects of ageing and neurological damage.

The trial involved 86 women with mild memory problems, known as mild cognitive impairment - and a common risk factor for dementia.

The women aged between 70 and 80 years, who were living independently at home, were split into three groups.

They were assigned to twice weekly hour long aerobic sessions of brisk walking; or resistance training, such as lunges, squats, and weights; or balance and muscle toning exercises (the control group).

Altogether 29 of the women had before and after MRI scans, which showed the hippocampus was significantly bigger in those completing six months of aerobic training compared with balance and muscle toning exercises.