How starting exercise in your 40s can reduce dementia risk by nearly half

A major long-term study tracking adults for 37 yrs finds that regular physical activity in your 40s, 50s and beyond can cut dementia risk by up to 45 per cent, even in those with genetic vulnerability

Staying active in your 40s and beyond may cut your risk of dementia by as much as 45 per cent, according to a new study.

 

Published in JAMA Network Open and titled Physical Activity Over the Adult Life Course and Risk of Dementia, the study shows that higher physical activity in midlife and late life offers strong protection against dementia, including Alzheimer’s disease.

 

The study followed more than 4,000 adults for 37 years and tracked multiple generations of participants since the 1970s. The participants were grouped into three life stages based on the age at which their physical activity was measured:

• Early adulthood: 26–44 years
• Midlife: 45–64 years
• Late life: 65–88 years

Over this period, 567 people developed dementia, with the majority of cases appearing in midlife and late-life participants.

So when does exercise actually protect the brain?

The strongest protective effects were seen in:

• Midlife (45–64 years)
• Late life (65+ years)

People in the top tiers of physical activity at these ages had 41–45 per cent lower risk of dementia compared with the least active participants. The effect held even after adjusting for major risk factors such as blood pressure, weight, diabetes, smoking, high cholesterol, education, and genetics.

 

In contrast, being active in one’s 20s and 30s did not significantly influence dementia risk later on within this dataset. This may be because dementia develops much later, making early-adulthood activity harder to link directly to outcomes.

Does the type of exercise matter?

According to the researchers, the type of exercise matters in midlife but less in later years.

 

In midlife, moderate to heavy physical activity was clearly protective, from brisk walking and cycling to more vigorous workouts. Higher-intensity midlife activity reduced dementia risk by up to 38 per cent.

 

But in late life, all activity, be it light, moderate or heavy, was linked with lower dementia risk. Once you cross 65, any movement is better than being sedentary.

What if someone has a genetic risk for Alzheimer’s?

The APOE ε4 allele is a well-known genetic risk factor for Alzheimer’s. The study found:

• In midlife: Exercise lowered dementia risk mainly for people without APOE ε4
• In late life: Exercise lowered risk for both carriers and non-carriers

Late-life APOE ε4 carriers with the highest activity levels had up to 66 per cent lower dementia risk.

 

This means even those genetically predisposed can meaningfully reduce risk, especially by staying active after 65.

Why does exercise help the brain?

Scientists believe physical activity protects the brain through several pathways:

• It improves blood flow to the brain
• It reduces chronic inflammation
• It boosts neurotrophic factors that support neuron growth
• It improves vascular health
• It helps regulate glucose and insulin sensitivity
• It may slow accumulation of proteins linked to Alzheimer’s

The researchers stress that whether it is brisk walking, dancing, gardening, cycling, gym workouts or swimming, consistency matters more than perfection. The study reinforces that it is almost never too late to start. 

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