Incidence of dementia: does gender make a difference?

Several studies suggested that women are at higher risk of dementia than men. However, that was based on rather limited data. We investigated possible gender differences in the incidence of dementia, Alzheimer's disease and vascular dementia, in the Rotterdam Study, a large population based prospective cohort study in the Netherlands of 7,046 persons aged 55 years and older, free of dementia at baseline. In 40,441 person-years of follow-up (mean 5.7 years) we identified 395 new cases of dementia (overall incidence: 9.8 per 1,000 person-years). Alzheimer's disease was the most frequent subtype of dementia (293 cases; 7.2 per 1,000). Vascular dementia was diagnosed in 57 participants (1.5 per 1,000). Overall, dementia incidence was similar for men and women (rate ratio women versus men: 1.00, 95% CI: 0.80-1.24). However, after 90 years of age dementia incidence declined in men but not in women (rate ratio 2.61, 95% CI: 1.04-6.56), in particular for Alzheimer's disease (rate ratio 5.79, 95% CI: 1.40-23.90). The overall incidence of vascular dementia was lower in women than in men (rate ratio 0.57, 95% CI: 0.34-0.97). This large population-based study suggests no gender differences in the incidence of dementia up to high age. After 90 years of age the incidence of Alzheimer's disease is higher for women than for men. The incidence of vascular dementia is higher for men than for women in all age groups.