Education has a long-lasting protective effect in cognitive aging
Helsinki, Finland - A recent study investigating the cognitive health of nonagenarians in Finland suggests that higher educational attainment may offer a sustained protective effect against cognitive decline, even into very old age. The research, published in PLOS One, followed a cohort of individuals for nearly five decades, observing associations between midlife and old-age cardiovascular risk factors, education, and cognitive performance at 90 years and older.
The study, which included 96 participants aged 90-97 from the older Finnish Twin Cohort, utilized data collected over 48 years. Researchers assessed various cardiovascular risk factors—including blood pressure, body mass index (BMI), physical activity, and cholesterol—through questionnaires administered in 1975, 1981, 1990, and 2021-2023. Educational attainment was self-reported. Cognitive function at age 90+ was measured using semantic fluency, immediate and delayed recall from a 10-word list learning task, and a composite cognitive score.
Anni Varjonen, from the Institute for Molecular Medicine Finland (FIMM) at the University of Helsinki, and her colleagues conducted regression analyses to determine how dementia risk factors predicted cognition at 90+ years, adjusting for age, sex, education, follow-up time, and APOE genotype.
The findings indicate a clear association between higher education and better cognitive performance across all measures. Participants with more years of education consistently showed superior scores in semantic fluency, immediate recall, delayed recall, and the composite cognitive score. This aligns with previous research on younger cohorts and reinforces the idea that education contributes to cognitive resilience throughout life.
Interestingly, the study also revealed complex and somewhat paradoxical associations with blood pressure. Individuals who reported high blood pressure in midlife (1975) scored significantly higher in semantic fluency, immediate recall, and delayed recall tests compared to those with normal blood pressure at that time. They also exhibited higher composite cognitive scores. Conversely, those with high blood pressure in very old age (2020-2023) scored lower in semantic fluency and the composite cognitive score, though not in immediate or delayed recall.
The researchers note that the unexpected association between midlife high blood pressure and better cognition in very old age might be influenced by factors such as early use of antihypertensive medications, which was common among the high BP group in midlife. It is also possible that these findings reflect reverse causality or selection bias within the small sample, particularly given that in 1970s Finland, awareness of high blood pressure was lower, potentially leading to misclassification.
Other cardiovascular risk factors, such as BMI, physical activity, and cholesterol levels, as well as the CAIDE (Cardiovascular Risk Factors, Aging, and Dementia) score, did not show consistent significant associations with cognition at 90+ years. This suggests that while these factors are important for dementia risk in younger old adults, their role in cognitive health may differ in individuals reaching very old age.
The educational-occupational score, a proxy for cognitive reserve reflecting lifelong exposure to intellectually demanding environments, was also positively associated with all cognitive measures at 90+ years. This further supports the notion that sustained intellectual engagement may build resilience against age-related cognitive decline.
The study acknowledges several limitations, including the small sample size and limited statistical power, which necessitate cautious interpretation of the findings. The "healthy survivor effect," where individuals living past 90 years old often have better health profiles, may also influence the results and potentially lead to spurious associations.
Despite these limitations, the research contributes to the understanding of cognitive aging by providing long-term follow-up data from a unique cohort. The sustained protective effect of education on cognition at 90+ years highlights its importance as a modifiable factor in promoting cognitive health. Future research with larger and more diverse populations is needed to confirm these findings and further investigate the intricate interplay between early-life factors, cardiovascular health across the lifespan, and cognitive outcomes in extreme old age.
