For women, physical fitness in midlife may do more than give the heart a boost; it may also benefit the brain, a new study from Sweden suggests.

Researchers found that middle-age women in Sweden with a high degree of cardiovascular fitness were nearly 90 percent less likely to develop dementia later in life than those who had a moderate fitness level. The findings were published (March 14) in the journal Neurology.

What’s more, if women in the fittest category did develop dementia, these problems — such as trouble with memory and thinking — tended to emerge, on average, 11 years later than among women in the moderate fitness group. So, the onset of dementia may have occurred at age 90 in a woman who was considered extremely fit woman at midlife, compared with age 79 in a moderately fit woman.

The findings suggest that high cardiovascular fitness is associated with a decreased risk of dementia, said lead author Helena Horder, a researcher at the Centre for Aging and Health at the University of Gothenburg in Sweden. In other words, good heart health is linked with good brain health, she said.

In the study, researchers looked at data from 191 women in Sweden ages 38 to 60. At the start of the study, in 1968, all of the middle-age women were given an exercise test on a stationary bike in which they cycled until they felt exhausted.

After tracking the women for 44 years, the researchers found that those fitness test scores helped predict whether the women would be diagnosed with dementia later in life. 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.

But the highest dementia rates were seen in women who started the exercise test but could not complete it: 45 percent of these women went on to develop dementia. The researchers suspect that some underlying cardiovascular processes — such as high blood pressure— in middle age might have made these women more vulnerable to dementia decades later.

Although the findings found an association between cardiovascular fitness and the risk of dementia, this study did not establish a cause-and-effect relationship between the two, the researchers said. It’s not clear why a woman’s fitness level at midlife might reduce her likelihood of dementia

It could be that improved fitness has a protective effect by reducing various cardiac risk factors, such as lowering blood pressure, creating a healthier body weight and producing a better lipid profile, Horder told Live Science. Emerging evidence also suggests that cardiovascular fitness may directly affect structures in the brain, by increasing blood flow to them, she noted.

Previous studies have established a connection between fitness and dementia, but some of them relied on people’s self-reported levels of physical activity and did not involve exercise testing. In studies that have shown a link between physical activity and dementia, it’s not clear whether the mechanism that may be responsible for the brain benefits is an enriched social environment and cognitive stimulation or the actual improvement in fitness level, Horder said.

One of the strengths of the new study is its long follow-up period from middle age to the golden years. But the researchers acknowledged that the study had limitations. For example, because the research looked at only Swedish women, the results may not be generalizable to other populations. In addition, the study was relatively small, with fewer than 200 women, and it evaluated cardiovascular fitness at only one point in time using an exercise test that may be done differently now than it was in 1968.

However, because there is not yet a cure for dementia, efforts, in general, have also focused on ways to modify people’s behaviors to potentially delay or prevent the condition’s onset, Horder said. Based on these and other findings, improved cardiovascular fitness through physical activity may be one of these potential approaches, she noted.

An editorial accompanying the new study suggested that additional research is needed to determine whether the link between fitness and dementia is due solely to the influence of heart health on brain health, or whether physical activity influences the brain independently of the activity’s cardiovascular effects. But the editorial ultimately concluded that “What is good for the heart really does seem to be good for the brain also.”

Originally published on Live ScienceBy Cari Nierenberg, Live Science Contributor