NEW YORK (Reuters Health) – Long-term strenuous activity may cut the risk of breast cancer in women, but may have a harmful effect on cognition, according to study findings presented Tuesday at the International Conference on Alzheimer’s disease in Vienna, Austria.

“The biggest finding,” lead researcher Dr. Mary C. Tierney told Reuters Health, “is that for every measure of cognitive ability (there were 11 different measures of memory, attention, language and cognitive flexibility), the more strenuous activity that a woman engaged in between high school and menopause, the lower her cognitive score.”

By contrast, long-term moderate physical activity was linked to improved cognition in later life, according to Dr. Tierney, a researcher with the University of Toronto.

Dr. Tierney said that prior research “lead to the question that if strenuous activity lowers breast cancer risk because it lowers estrogen levels and we know estrogen is essential for normal cognitive function in women, then will strenuous activity throughout life have an adverse effect on cognition?”

To answer this, the researchers surveyed 90 postmenopausal women regarding the amount of strenuous and moderate physical recreational activities they participated in from high school to menopause. Memory and frontal lobe functioning were assessed using standard neuropsychological tests.  

As noted, cognitive ability on all measures was inversely linked to the amount of strenuous physical activity. Statistically significant associations were seen with semantic memory, working memory, delayed verbal recall, and sustained attention.

Moderate physical activity, by contrast, was tied to enhanced cognitive performance. Associations with cognitive flexibility, working memory, and sustained attention reached statistical significance.

The results confirm prior research showing “the beneficial cognitive effects of activity but adds critically important information that the intensity of the activity is a very important factor in cognitive outcome,” Dr. Tourney said.

Larger studies are needed to confirm these findings and also to investigate whether a similar association is seen in men, she added.