Regardless of ethnicity, women worldwide have a higher risk for dementia than men, suggesting that sex differences may influence dementia risk, according to study findings published in Alzheimer’s & Dementia.
Researchers in 18 countries across the world conducted 21 studies as part of the Cohort Studies of Memory in an International Consortium (COSMIC) collaboration to assess whether sex differences across a diverse, multi-ethnic, and international cohort influenced dementia risk. The studies encompassed 29,850 participants.
Following a median follow-up of 4.6 years, 2089 participants developed all-cause dementia, most (n=1442) of whom lived in Western countries, comprising 8.6% of participants from those countries. A total of 306 cases among 8031 participants were reported in Asia (3.8%) and 341 cases in 5075 participants from other countries (6.7%). Approximately 66% of individuals with all-cause dementia were women.
Incidence rate of dementia among women totaled 16.4 per 1000 person-years and 12.3 per 1000 person-years in men. Participants aged 80 and older demonstrated higher incidence rates of dementia.
After pooling data from the 21 studies together, women demonstrated higher risk for all-cause dementia than men after adjusting for age and education (hazard ratio [HR], 1.12; 95% CI, 1.02-1.23). Compared with men living in the same countries, women living in countries with low to lower-middle income economies exhibited even higher risk for dementia (HR, 1.73; 95% CI, 1.25-2.39; P =.03).
When assessing various risk factors for dementia, the researchers discovered that similar associations existed in both men and women. Older age, diabetes, depression, hearing deficits, and being carriers of the apolipoprotein E (APOE ε4) gene predisposed both sexes to increased dementia risk. Higher educational status, higher physical activity levels, current alcohol use, and higher hip circumference correlated with lower risk for dementia in both men and women.
Compared with women, men with lower body mass index demonstrated a lower dementia risk (HR, 0.88; 95% CI, 0.83-0.93) and men with higher low-density lipoprotein (LDL) cholesterol levels (HR, 1.07; 95% CI, 1.02-1.13) had a higher dementia risk.
Overall, the researchers highlighted that the greatest risk for dementia was seen among women, which contributes to evidence that sex differences in dementia risk do exist among men and women. Moreover, they noted that these differences are more heightened in poorer countries.
They concluded, “Given the diverse socio-political, socioeconomic, and cultural contexts across the world, these findings justify ongoing efforts to support programs to improve sex and gender equity in brain health throughout the life course, particularly in the populace from underrepresented settings.”
The study has several limitations, including a lack of exact timing of dementia diagnosis, potential missed prodromal dementia cases or misclassified dementia cases, lack of assessment based on dementia subtypes such as Alzheimer disease and vascular dementia, and the observational design of the study, which precludes causality.
Disclosures: Several study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see original source for full list of disclosures.
Gong J, Harris K, Lipnicki DM, et al. Sex differences in dementia risk and risk factors: individual-participant data analysis using 21 cohorts across six continents from the COSMIC consortium. Alzheimers Dement. Published online February 15, 2023. doi:10.1002/alz.12962