March 21, 2018

This one factor may cut dementia risk by 90%—but researchers stress it's too early to tell

Daily Briefing

    High cardiovascular fitness in middle-aged women is associated with a nearly 90% decline in the risk of developing dementia, according to a study published Wednesday in Neurology.

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    Study details

    For the study, researchers evaluated the association between cardiovascular fitness and dementia risk in a subsample of 191 women, ages 38 to 60, who enrolled in the Prospective Study of Women, which started in Sweden in 1968. At the start of the study, women completed an ergometer cycling test to evaluate their cardiovascular fitness. They were broken into one of three groups:

    • High cardiovascular fitness (40 women);
    • Low cardiovascular fitness (59 women); and
    • Moderate cardiovascular fitness (92 women).

    Over the next 44 years, the women were tested for dementia six times.

    Limitations of the study include the small study population and the observational design—which prevents the researchers from demonstrating a causal relationship between cardiovascular fitness and dementia.

    Findings

    From 1968 to 2012, 23% of study participants developed dementia. The researchers found middle-aged women with a high level of cardiovascular fitness had an 88% lower risk of developing dementia when compared with moderately fit middle-aged women.

    Further, according to the study, the women with a high level of cardiovascular fitness who developed dementia did so later in life. Specifically, the researchers found highly fit women developed dementia at 90, whereas women with a moderate level of cardiovascular fitness developed dementia at 79.

    The researchers concluded "improved cardiovascular fitness might be a modifiable factor to delay or prevent dementia." They wrote, "Promotion of a high cardiovascular fitness may be included in strategies to mitigate or prevent dementia." However, they wrote, "Findings are not causal, and future research needs to focus on whether improved fitness could have positive effects on dementia risk and when during the life course a high cardiovascular fitness is most important."

    Comments

    Helena Hörder, the study's lead investigator and a professor in the Department of Psychiatry and Neurochemistry at the University of Gothenburg in Sweden, said, "These findings are exciting because it's possible that improving people's cardiovascular fitness in middle age could delay or even prevent them from developing dementia."

    Rong Zhang of the University of Texas Southwestern O'Donnell Brain Institute said despite the study's small sample size, the findings are consistent with previous research, offering "additional evidence that what's good for the heart is good for the brain."

    However, Nicole Spartano of Boston University School of Medicine and Tiia Ngandu of Karolinska Institutet Center for Alzheimer Research in an editorial accompanying the study in Neurology raised questions about the study. They wrote, "We must determine whether these associations are due solely to the influence of heart health on brain health or whether exercise influences the brain independently of cardiovascular effects." They continued, "There is a need for longer-term intervention studies to understand whether exercise training, possibly even at modest doses and intensity can improve dementia risk."

    Keith Fargo, director of scientific programs and outreach for the Alzheimer's Association who was not involved in the study, said, "One of the missing pieces of a study like this—and really the weakness in the literature to date—is that the kinds of studies that we have mostly seen are association studies," as opposed to studies that show cause.

    However, Fargo 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." He added, "The demand for nutrient-, oxygen-rich blood in the brain is very high compared to other organs, and so anything a person can do to increase their cardiovascular fitness level is likely to have positive benefits on brain health" (McNamara, Medscape, 3/16; Howard, CNN, 3/14; Weintraub, USA Today, 3/14; Hörder et al., Neurology, 3/14).

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