A large Norwegian study of 1,491 adults aged 70–77 found that those with higher cardiorespiratory fitness had roughly half the risk of developing Alzheimer's disease over nearly nine years compared to unfit peers. Researchers measured peak oxygen uptake (VO2peak) directly and found that staying above 80% of the sex-specific average — about 25 mL/kg/min for men and 21 mL/kg/min for women — was a meaningful threshold below which Alzheimer's risk rose substantially. Each 1 mL/kg/min increase in VO2peak was linked to a 4% reduction in risk. Interestingly, short-term fitness improvements over just one year did not significantly change the risk, suggesting that building and maintaining fitness before reaching old age matters most.
