Study with twins associates higher educational attainment with better cognitive performance in old age

For decades, science has attempted to unravel the secrets of cognitive aging. It has been proven over the years that a higher level of education contributes to slowing mental decline and delaying the onset of neurodegenerative diseases. What allows some people to reach old age with a lucid mind while others face early decline? Although the risk of dementia has been widely studied in adults over 65, little is known about what promotes cognitive health in people who reach 90.

In search of answers, a team of researchers from the Institute for Molecular Medicine in Finland embarked on a scientific journey that spanned nearly half a century. Following a cohort of twins starting in 1975, a new study published this Wednesday in the journal PLOS One reveals findings that were as long-awaited as they are surprising. The scientists followed 96 people, all born before 1933 and now between the ages of 90 and 97. They assessed multiple variables, from blood pressure and cholesterol to physical activity levels, as well as dementia risk scores.

The results were clear. Those with a higher educational attainment—12 or more years of schooling—and higher scores on the Educational and Occupational Index performed better on all cognitive tests, including verbal fluency and memory. Surprisingly, participants who had high blood pressure in middle age showed better cognitive performance in old age. This unexpected association also surprised lead author Anni Varjonen. “There are several reasons why we think this might be the case. Of course, the first is that we had a very small group of people who reported having high blood pressure, and that can always make the statistical analysis less reliable,” she acknowledged to EL PAÍS.

The sample of twins where both reached 90 years of age was limited—only 13 pairs—and most of them shared similar lifestyles, which limited the analysis of genetic differences. Furthermore, hypertension in old age did show a negative relationship with semantic fluency. The study, on the other hand, points out several limitations, such as the small sample size, the possible selection of “healthy survivors”—that is, people who live longer and are healthier than the general population—and the limited statistical power to detect more subtle effects. Coral Sanfeliu, an expert in brain aging and a researcher at the Barcelona Institute for Biomedical Research, believes that the study’s findings warrant caution. “Although interesting, the results should be interpreted with caution. Further research is needed to confirm and better understand the observed relationships,” notes this expert, who was not involved in the analysis.

Physical activity in midlife also showed a modest positive association with verbal fluency, but not with other cognitive functions. Other cardiovascular factors, such as Body Mass Index and cholesterol, showed no significant associations with mental performance in the ninth decade of life. “This shouldn’t discourage us. Maintaining a healthy lifestyle, along with exercise, a good diet, and restful sleep, remains essential,” adds Sanfeliu.

The importance of learning

To date, education remains the most robust factor in the fight against cognitive decline, although this aspect remains under debate. In 2017, researchers at the University of Mashhad (Iran) identified a relationship between educational attainment and resistance to developing Alzheimer’s disease. Another recent analysis in the journal Nature, conducted with participants from 33 countries, indicates that early schooling improves intellectual abilities throughout life, but does not appear to affect the rate of decline or structural aging of the brain.

Scientists led by Anni Varjonen indicate that educational attainment can also reflect variables not directly measured, such as cognitive ability in childhood or socioeconomic status. Still, for them, the link between education and later cognitive function appears to stand the test of time. “It wasn’t the focus of our study, but in my opinion, it can certainly have an impact. I think it would be very positive to have cognitive stimulation throughout life, and it would definitely benefit brain health,” Varjonen notes.

In contrast, cardiovascular factors, although relevant in earlier life stages, appear to have a more modest influence on cognition after age 90. At least in this study. Professor Ignacio Morgado of the Institute of Neuroscience at the Autonomous University of Barcelona points out that although this is a long-term analysis, it is more of a “correlation.” “What is clear in the study is that education remains a lasting protective factor,” he maintains.

“We hope to continue recruiting more participants as they turn 90, so we may be able to have larger sample sizes in the future and continue working with 90-year-old twins to learn more about their brain health,” the lead researcher concludes.

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