I read with great interest the paper by Yamada et al.1 In their study, they stated that the prevalence of Alzheimer's disease (AD) was two times higher in women than in men, while vascular dementia (VD) was the same in both sexes. In their study, however, 20 out of 46 (43.5%) demented men were younger than 80 years and 41 of 142 (28.9%) demented women were younger than 80 years. They also stated that the incidence of VD might decrease as the risk of stroke decreased because the recent prevalence of VD and the incidence of stroke had decreased in the Hisayama Study.2
Since the survival rate of AD is higher compared to the rate of VD,3,4 women may have the greater prevalence of AD because they live longer than men. I would like to ask Yamada et al. to show age- and sex-specific prevalence of AD, as it may be helpful for readers to know whether women have higher age-adjusted prevalence of AD compared with men.