Background <p>Women have a greater lifetime risk of developing dementia. Despite clear sex differences, studies investigating modifiable dementia risk factors often overlook differences between sexes and age. This study examined sex and age differences in the prevalence of modifiable dementia risk factors and their associations with cognition.</p> Methods <p>Participants were from the Health and Retirement Study, a nationally representative cohort study. Thirteen risk factors were examined, including education, hearing loss, cholesterol, depression, physical inactivity, diabetes, smoking, hypertension, obesity, excessive alcohol use, social isolation, poor vision, and poor sleep. A global cognitive summary score was also examined. Chi-square and t-tests examined sex and age differences in prevalence; linear regression examined interactions between sex, age, and risk factors on cognition.</p> Results <p>This study included 17,182 participants with a mean age of 69.2 ± 10.6 years, 59.2% of which were women. Ten out of 13 risk factors had sex differences in prevalence. Women had higher prevalence of elevated cholesterol, depression, physical inactivity, smoking, poor vision, and poor sleep. Women also had fewer years of education. Men had a higher prevalence of hearing loss, diabetes, and excessive alcohol use. Hearing loss, diabetes, and hypertension were associated with greater effects on cognitive performance in woman than men. BMI was negatively associated with cognitive performance in women compared to men in their 50s and 60s, but not at older ages. Education and cholesterol had stronger, positive associations with cognitive performance in women compared to men.</p> Conclusions <p>These data suggest that women’s greater risk of dementia may be due to a higher prevalence of multiple risk factors and stronger cognitive effects of risk factors. Results may inform future personalized prevention strategies for dementia risk reduction, particularly in women.</p>