Women with high cardiovascular fitness in midlife were 88 percent less likely to develop dementia than moderately fit women, according to long-term research from the University of Gothenburg published in the medical journal Neurology.
The fitness measurement came from a bicycle exercise test in which participants pedaled at increasing resistance until exhaustion.
Women who reached at least 120 watts of peak workload were classed as highly fit. The average age at the start of the study was 50, and researchers tracked the group with six dementia assessments over four decades.
Only 5 percent of the highly fit women went on to develop dementia. That compared with 25 percent among the moderately fit group and 32 percent among those with low fitness.
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Among women who had to stop the exercise test early because of chest pain, high blood pressure or other issues, 45 percent developed dementia decades later.
When highly fit women did develop dementia, the diagnosis came on average 11 years later than in moderately fit peers, at age 90 instead of age 79.
Why cardio may protect the aging brain
Cardiorespiratory fitness reflects how efficiently the heart, lungs and blood vessels deliver oxygen during sustained exercise.
Researchers think that vascular benefit reaches the brain as well, supporting steady blood flow, healthier small vessels and better clearance of waste products tied to Alzheimer's.
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A newer analysis backs the pattern. A 2026 study of nearly 11,000 adults in the Cooper Center Longitudinal Study, published in JACC: Advances, found that people with high cardiorespiratory fitness had a 31 percent lower risk of later-life dementia than those with low fitness.
The authors reported that fitness and cumulative vascular injury act through complementary, non-overlapping paths in the way dementia develops.
Related research suggests that regular aerobic activity may also help the brain clear the waste products linked to Alzheimer's.
What the numbers mean for your week
The Swedish study is observational, so it cannot prove that becoming fitter directly prevents dementia.
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The women were all enrolled in the late 1960s in Gothenburg, which the authors note may limit how far the results apply to other groups. The 88 percent figure compared high fitness with medium fitness, not with any single lifestyle change.
Federal guidance offers a concrete weekly target.
The Centers for Disease Control and Prevention advises adults to get at least 150 minutes of moderate-intensity aerobic activity, such as brisk walking, or 75 minutes of vigorous-intensity activity, such as running, each week, plus muscle-strengthening work on at least two days.
Anyone with heart disease, joint problems or a long gap since their last workout should talk with a doctor before starting a vigorous program.
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This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.