Among centenarians and near-centenarians, education level may be a protector against dementia, according to an individual participant data meta-analysis published in Alzheimer’s & Dementia.
In the coming 30 years, the population of individuals aged 100 years or older is estimated to be 2.2 million. With an increasing centenarian and near-centenarian population, health care systems will experience an increased burden caring for these individuals who will likely have some degree of disease and/or disability.
For the study, researchers sought to evaluate risk and protective factors associated with dementia in the centenarian and near-centenarian population. To that end, researchers from the International Centenarian Consortium-Dementia (ICC-Dementia) sourced data from 18 international community-based studies of centenarians and near-centenarians for this participant-level meta-analysis. Cognitive impairment was defined as Mini-Mental State Examination (MMSE) of 22 or lower.
The study population comprised 4427 individuals aged 95 (mean, 98.3) years or older, 79% were women, and they were living in 11 countries.
Overall, the study participants had MMSE scores ranging from 15.73 to 26.43. The proportion of men and women aged 95-99 years who had cognitive impairment were 35.0% and 39.6% and those who were aged 100 years or older were 58.0% and 65.0%, respectively.
For functional impairment, according to the Activities of Daily Living (ADL) instrument, most had impairments in over 2 domains. The proportion of men and women aged 95-99 years who had 1 or more functional impairment were 66.7% and 65.9% and 84.9% and 92.4% for individuals aged 100 years or older, respectively.
Dementia was observed among:
- 34.0% of men aged 95-99 years,
- 38.4% of women aged 95-99 years,
- 55.8% of men aged 100 years or older, and
- 64.8% of women aged 100 years or older.
Of note, studies with convenience sampling reported a lower prevalence of dementia than population-based studies.
In a pooled logistic regression analysis, dementia and cognitive impairment were negatively related with age and female gender and positively related with years of education. Functional impairment was related with only age and gender and not education.
After controlling for age, gender, and education, individuals who lived in an institution were found more likely to present with dementia or to be cognitively or functionally impaired compared with centenarians and near-centenarians residing in a community.
The only medical history variable that had some relationship with cognitive and functional impairment in extreme late life was hypertension (odds ratio [OR], 0.51; 95% CI, 0.35-0.74).
Overall, the researchers found that around half of the centenarian and near-centenarian population was free from dementia. Further, they found that “Education was protective against dementia, but other factors for dementia-free survival in C/NC [centenarians and near-centenarians] remain to be understood.”
The findings of this analysis may have been limited as the studies did not use the same versions of the MMSE or ADL instruments.
Disclosure: Multiple authors declared affiliations with industry. Please refer to the original article for a full list of disclosures.
Leung Y, Barzilai N, Batko-Szwaczka A, et al. Cognition, function, and prevalent dementia in centenarians and near-centenarians: An individual participant data (IPD) meta-analysis of 18 studies. Alzheimers Dement. Published online December 1, 2022. doi:10.1002/alz.12828