Dementia is expected to affect an estimated 150 million people globally by 2050 (Nichols et al, 2019). The Lancet Commission on dementia prevention previously calculated that up to 40% of cases of dementia may be preventable through 12 potentially modifiable risk factors (Livingston et al, 2020). In the absence of available disease-modifying treatments for dementia, understanding these risk factors is essential to address this public health challenge and guide preventive practices.
Previous research has suggested that women may be at an increased risk of dementia, but this evidence is conflicting and has mainly been conducted in High-Income Countries (HICs) (Nebel et al, 2018). Currently, 60% of people with dementia live in low-and-middle income countries (LMICs), and this is projected to increase to 80% by 2050 (Prince et al, 2007). However, the association between sex and dementia risk in these settings is not well understood. Furthermore, many studies of potentially modifiable dementia risk factors adjust for sex as a covariate, so it is unknown whether their effects vary according to sex.
To address these gaps in the research, Gong et al (2023) conducted an individual participant data meta-analysis using a diverse, global population from 21 cohorts to investigate whether there is a sex difference in the overall risk of all-cause dementia and whether sex influences the impact of risk factors for dementia.
The study re-analyzed individual participant data from the 21 cohorts of the COSMIC collaboration to understand sex differences in dementia risk and rate. The authors calculated hazard ratios for sex as a risk factor for all-cause dementia, sex-specific hazard ratios for each Lancet Commission 2020 risk factor and the risk of all-cause dementia, and conducted subgroup analyses to explore sex differences in risk factors.
Results from 29,850 participants across 18 countries revealed that the incidence rate of dementia was higher in women than in men. The study also found sex differences in the impact of certain risk factors for dementia, such as body mass index, cholesterol levels, and alcohol use.
The authors concluded that a greater risk of dementia for women was observed, contributing to accumulating evidence for sex differences in dementia risk. They also observed that the excess dementia risk in women was more pronounced in poorer countries.
While the study had geographic and ethnic diversity, allowing for global representativeness and increased precision of estimates, variability in dementia definitions, measurement tools, and population characteristics across the cohorts was a limitation. Additionally, some risk factors lacked sufficient data for analysis, and there was high variability in effect estimates for sex and dementia risk among the cohorts.
In summary, the study provides valuable insights into sex differences in dementia risk and the impact of risk factors, especially in diverse, global populations. This research underscores the need for ongoing efforts to address sex and gender equity in brain health.
