Moderate caffeinated coffee consumption (2–3 cups per day) in middle-aged and older adults is associated with an 18–19% reduced risk of dementia, with no such association observed in women, with decaffeinated coffee, or at intakes below 2 cups per day.

Study: Associations Between Different Coffee Types, Neurodegenerative Diseases, and Related Mortality: Findings from a Large Prospective Cohort Study.

People who drank three or more cups of regular coffee a day were less likely to get dementia than those who didn’t drink coffee, but decaf coffee didn’t help. The study didn’t check if this was true for women or exactly how much coffee is best.

Study: Coffee and Tea Intake, Dementia Risk, and Cognitive Function.

The study found that people who drink 2–3 cups of caffeinated coffee a day have a lower risk of dementia, just like the claim says — but it also found this benefit happens in both men and women, not just men, so the claim is wrong about women.

Study: Association of coffee and genetic risk with incident dementia in middle-aged and elderly adults

This study found that drinking a certain kind of caffeinated coffee (ground coffee) might lower dementia risk, but drinking decaf coffee was linked to higher risk — the opposite of what the claim suggests. It also didn’t confirm the exact 18–19% benefit or say anything about women.

Study: High coffee consumption, brain volume and risk of dementia and stroke

This study found that drinking a lot of coffee (more than 6 cups a day) might increase dementia risk, and the safest amount was just 1–2 cups—not 2–3 as the claim says. It also didn’t check if women benefit differently, so it doesn’t support that part either.