Women who are physically active at any point during their lives have a lower risk of cognitive impairment later in life, however physical activity during adolescence appears to be the most important, the results of a new study indicate.

There is already growing evidence that people who are physically active in mid and late life have a lower chance of developing dementia and more minor forms of cognitive impairment in old age. However, there is a poorer understanding of the importance of early life physical activity and the importance of activity at different ages.

Canadian researchers looked at over 9,300 women, comparing their physical activity levels during adolescence, at the age of 30, at the age of 50 and later in life.

Of the participants, 15% said they were inactive as teenagers, 29% were inactive at the age of 30, 28% were inactive at the age of 50 and 21% were inactive in late life.

While being inactive at any age appeared to be linked to cognitive impairment later in life, when different factors were taken into account, such as body mass index (BMI), high blood pressure, smoking and depressive symptoms, only teenage inactivity remained significantly associated with cognitive performance in old age.

"Our study shows that women who are regularly physically active at any age have a lower risk of cognitive impairment than those who are inactive, but that being physically active as teenagers is most important in preventing cognitive impairment," explained lead researcher, Dr Laura Middleton of Sunnybrook Health Sciences Centre.

The study also found that women who were physically inactive teenagers, but became physically active at age 30 and age 50, had significantly reduced odds of cognitive impairment relative to those who remained physically inactive.

In contrast, being physically active at age 30 and age 50 was not significantly associated with rates of cognitive impairment in those women who were already physically active teenagers.

"As a result, to minimise the risk of dementia, physical activity should be encouraged from early life. Not to be without hope, people who were inactive as teenagers can reduce their risk of cognitive impairment by becoming active in later life," Dr Middleton said.

The researchers concluded that the mechanisms by which physical activity across the life course is related to late life cognition are likely to be multi-factorial.

There is evidence to suggest that physical activity has a positive effect on brain plasticity and cognition and in addition, physical activity reduces the rates and severity of vascular risk factors, such as high blood pressure, obesity and type 2 diabetes, which are each associated with an increased risk of cognitive impairment.

"Low physical activity levels in today's youth may mean increased dementia rates in the future. Dementia prevention programmes and other health promotion programmes encouraging physical activity should target people starting at very young ages, not just in mid and late life," Dr Middleton added.

Details of these findings are published in the Journal of the American Geriatrics Society.

For more information: www.irishhealth.com