According to a large international study on dementia risk, which included nearly 30,000 participants from 18 countries across all six continents, social and economic disadvantage may account for the increased likelihood of women developing the condition.
While there was minimal evidence of sex-based variations in the majority of recognized risk factors for dementia, the elevated risk of women developing the illness was more pronounced in countries with lower socioeconomic status.
Lead author Jessica Gong, from The George Institute for Global Health, said that while previous research had shown women have a greater lifetime risk of developing dementia than men, partly because they tend to live longer, age alone may not fully account for this difference.
“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,” she said.
“We found that when adjusted for age, rates of dementia were highest among low- to lower-middle income countries, and higher in women than men.”
The number of people living with dementia is projected to exceed 150 million by 2050 worldwide, three times the 2019 estimate of 50 million. Rates are increasing most rapidly in low- and middle-income countries (LMICs) that are less able to manage the significant economic and societal impact of this devastating disease.
In 2020 the Lancet Commission Report estimated that as much as 40 percent of dementia risk could be attributed to 12 modifiable risk factors, many of which are more common in LMICs. They include less education, hypertension, obesity, diabetes, depression, hearing impairment, smoking, excessive alcohol consumption, physical inactivity, low social contact, traumatic brain injury, and air pollution.
“When we looked for sex differences in these risk factors, we found that, older age, diabetes, depression, hearing impairment, and having a certain genetic variation involved in fat metabolism in the brain – known as APOE4 – were associated with a greater risk of dementia in both women and men,” Ms. Gong said.
“While more years of education, higher hip circumference, current alcohol use (versus never drinking), and high physical activity (versus none to minimal activity) were associated with a lower risk of dementia in both sexes.
“But there was moderate evidence for a sex difference with years spent in education, indicating a stronger protective association for men than women.”
The authors argued that women, particularly in LMICs, have not had equal educational and occupational opportunities to men, and higher educational attainment and mentally stimulating occupations have been shown to be protective against dementia.
Associate Professor Sanne Peters, a Senior Lecturer at The George Institute for Global Health UK in partnership with Imperial College London and part of the research team, said that institutional factors restricting women’s opportunities reduced access to appropriate healthcare and risk management programs, as well as other factors such as domestic violence – particularly for women from lower socioeconomic settings – can lead to psychological stress and leave them in worse financial positions, affecting their late-life cognitive health.
“In general, the geographical patterns that we saw for increased dementia risk in women seemed to echo those of gender disparity,” she said.
“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.”
Reference: “Sex differences in dementia risk and risk factors: Individual-participant data analysis using 21 cohorts across six continents from the COSMIC consortium” by Jessica Gong, Katie Harris, Darren M. Lipnicki, Erico Castro-Costa, Maria Fernanda Lima-Costa, Breno S. Diniz, Shifu Xiao, Richard B. Lipton, Mindy J. Katz, Cuiling Wang, Pierre-Marie Preux, Maëlenn Guerchet, Antoine Gbessemehlan, Karen Ritchie, Marie-Laure Ancelin, Ingmar Skoog, Jenna Najar, Therese Rydberg Sterner, Nikolaos Scarmeas, Mary Yannakoulia, Mary H. Kosmidis, Antonio Guaita, Elena Rolandi, Annalisa Davin, Oye Gureje, Stella Trompet, Jacobijn Gussekloo, Steffi Riedel-Heller, Alexander Pabst, Susanne Röhr, Suzana Shahar, Devinder Kaur Ajit Singh, Nurul Fatin Malek Rivan, Martin van Boxtel, Sebastian Köhler, Mary Ganguli, Chung-Chou Chang, Erin Jacobsen, Mary Haan, Ding Ding, Qianhua Zhao, Zhenxu Xiao, Kenji Narazaki, Tao Chen, Sanmei Chen, Tze Pin Ng, Xinyi Gwee, Katya Numbers, Karen A. Mather, Marcia Scazufca, Antonio Lobo, Concepción De-la-Cámara, Elena Lobo, Perminder S. Sachdev, Henry Brodaty, Maree L. Hackett, Sanne A. E. Peters and Mark Woodward, for the Cohort Studies of Memory in an International Consortium (COSMIC), 15 February 2023, Alzheimer’s & Dementia.
Funding: UK Medical Research Council Skills Development Fellowship, Australian National Health and Medical Research Council, National Institute on Aging of the National Institutes of Health, French National Research Agency, Alzheimer’s Association, European Social Fund, Ministry of Health and Social Solidarity, Ministry of Higher Education, Fondo de Investigación Sanitaria, Instituto de Salud Carlos III, Spanish Ministry of Economy and Competitiveness, Fondo Europeo de Desarrollo Regional, National Institute on Aging, Swedish Research Council, Swedish Research Council RAM, Swedish Research Council for Health, Working Life and Wellfare, Hjärnfonden/Swedish Brain Foundation, Alzheimerfonden, Alzheimer’s Association Zenith Award.