Helena Hörder, Ph.D., from the University of Gothenburg in Sweden, and colleagues conducted a stepwise-increased maximal ergometer cycling test to evaluate cardiovascular fitness among a systematic subsample of 191 women.
It's well established that being fit is likely to protect your brain from dementia years from now, and a new study demonstrates how mighty that shield is. During that time, 44 of the women developed dementia. When highly fit women developed the disease, it came on average 11 years later than among those with moderate levels of fitness - at the age of 90 instead of 79.
Forty women met the criteria for a "high" fitness level, an average peak workload of 120 watts or higher, while 92 women were categorised as "medium".
The group was then tested for dementia six times over the following 44 years, during which time 44 developed dementia. 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. Women in the exercise test did not differ from the total sample in age or cumulative dementia incidence (23.0% versus 22.1%, P=0.780).
After adjusting for age, body height, triglycerides, smoking, hypertension, wine consumption, physical inactivity, and income, the researchers found that the hazard ratio for all-cause dementia was 0.12 (95% CI 0.03-0.54) among high-fitness women and 1.41 (95% CI 0.72-2.79) among low-fitness women, compared with women of medium fitness.
"Some of it may be the indirect effects of control in cardiovascular risk factors", Dr. Narula said. The highly fit women were 88 percent less likely to develop dementia than the moderately fit group. As the researchers point out, the women's fitness levels were only measured once so it doesn't confirm if they maintained or improved their fitness levels post-1968.
He said it raises people's awareness about the need to be physically fit, particularly in later life.
Dr Tim Shakespeare, from the Alzheimer's Society, said: "While the results are promising, and provide much-needed motivation to jump on the exercise bike, it's important to bear in mind the number of people in this study was small and it only involved women, so it's not clear if we'd see the same results in men".
The study was supported by the Forte-Centre Aging and Health: Centre for Capability in Ageing (AGECAP).