Very fit women are 90 per cent less likely to develop dementia than the least fit and those who do have it diagnosed years later, a study has found.
The study, published online by the journal Neurology, measured the women's cardiovascular fitness based on an exercise test.
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 Swedish research followed nearly 200 women from middle age until their nineties.
"I was not surprised that there was an association, but I was surprised that it was such a strong association between the group with highest fitness and decreased dementia risk", said Helena Hörder, a professor in the Department of Psychiatry and Neurochemistry at the University of Gothenburg in Sweden, who was first author on the study. So more research is also needed to determine whether improved fitness could have positive effects on dementia risk and when in life a high fitness level is most important.
For the study, 191 women with an average age of 50 took a bicycle exercise test until they were exhausted to measure their peak cardiovascular capacity. The average peak workload was measured at 103 watts.
A total of 40 women met the criteria for a high fitness level, or 120 watts or higher, while 92 women were in the medium fitness category. The analysis showed that 32 percent of the women with a low fitness score developed dementia during the study period, compared with 25 percent of those women with a medium fitness score and 5 percent of the highly fit women.
Still, he said, "the picture that is really emerging from the literature is a picture about the importance of fitness in midlife, not just old age, when it comes to protecting your brain health and preventing or delaying Alzheimer's disease and other dementias". The highly fit women were 88 percent less likely to develop dementia than the moderately fit women. "This might indicate that processes in the cardiovascular system might be ongoing many decades before onset of dementia diagnosis".
She said limitations of the study included the relatively small number of women involved, all of whom were from Sweden, so the results may not be applicable to other groups.
Dr Horder also pointed out that the women's fitness level was only measured once, so any changes in fitness over time were not incorporated.
The study was supported by the Swedish Forte Center on Aging and Health, the Swedish Research Council for Health, Working Life and Welfare, Alzheimer's Association Stephanie B. Overstreet Scholars, Alzheimer's Association Zenith Award, Sahlgrenska University Hospital, Bank of Sweden Tercentary Foundation, Swedish Brain Power and several Swedish foundations.
To learn more about dementia, visit www.aan.com/patients.