Research led by the George Institute for Global Health suggests that the increased risk for Alzheimer’s and other forms of dementia experienced by women compared with men is largely due to socioeconomic factors.
The team found no evidence of a significant sex difference in risk factors that could account for higher levels of dementia in women except for educational level. They also found higher levels of dementia in women in low-to-middle income countries compared with richer countries.
It is predicted that 150 million people will have some form of dementia by 2050. Previous studies have shown that women have higher rates of dementia than men. For example, according to one study the estimated risk of developing Alzheimer’s disease later in life is 20% for a 45 year old woman and 10% for a 45 year old man.
The Lancet Commission Report, published in 2020, suggested 12 risk factors contributed significantly to the risk of developing dementia later in life. These included: low education level, hypertension, obesity, diabetes, depression, hearing impairment, smoking, high alcohol consumption, physical inactivity, low social contact, traumatic brain injury, and air pollution.
Previous research has attributed the sex difference in dementia prevalence to the fact that women live longer than men, but Jessica Gong and colleagues from The George Institute for Global Health in the U.K. and Australia, wanted to test the impact of the different risk factors outlined by the Lancet report in different countries.
As reported in the journal Alzheimer’s & Dementia, 29,850 participants (58% women) from 21 cohorts across six continents were included in an individual participant data meta-analysis.
Over a median time of 4.6 years, 2089 individuals developed dementia. Of these, 66% were women. Overall, women were 12% more likely to develop dementia than men. This trend was particularly noticeable in women living in low- or middle-income countries who had a rate of dementia per 1000 person years of 26.3 vs 17.4 for women in high income countries.
In contrast, country-level income did not significantly impact dementia rates in men with rates of 13.7 and 13.8 per 1000 person years in high and low/middle income countries, respectively.
“Most research estimating dementia incidence to date has been conducted in high-income countries, with very little data available in the countries that actually bear the greatest burden,” noted first-author Gong in a press statement.
When individual risk factors were assessed, the authors found little difference between women and men. Older age, diabetes, depression, having a hearing impairment, and carriage of the APOE-E4 mutation increased risk in both sexes, whereas more years of education, increased hip circumference, current alcohol use (vs never), and high physical activity appeared to reduce risk.
The only exceptions were a difference in the impact of former alcohol use (vs never)—this seemed to increase risk by 18% in men but decrease risk in women—and the protective effect of education. Women gained 5% reduction in relative risk per year of education, whereas men gained 6%.
“In general, the geographical patterns that we saw for increased dementia risk in women seemed to echo those of gender disparity,” said Sanne Peters, a co-author and senior lecturer at the George Institute for Global Health in the U.K.
“These findings justify support for programs to improve gender equity in brain health throughout the life-course, particularly in populations that have been previously underrepresented in dementia research.”
