Study Strengths Claim That Late-in-Life Cognitive Activity Reduces Dementia Risk

Studies have suggested a protective effect between late-life cognitive activities, such as reading, playing games, and attending cultural events, and preventing or delaying the development of Alzheimer’s disease or other types of age-associated dementia. However, questions have been raised about whether these studies’ findings demonstrate an actual cause-and-effect relationship or if they are, rather, the result of unmeasured confounding factors.

A new study in the September 2016 issue of Epidemiology performed a bias analysis of previous studies showing positive effects from cognitive activity, and concluded that although potentially confounding factors might have affected results, it is doubtful that such factors totally account for observed associations between cognitive activities and a reduced risk of dementia. Researchers said the bias due to unmeasured factors was unlikely to account for all of the association because the impact of such factors is likely to be considerably smaller than the observed effect.

“While it is possible that socioeconomic factors such as educational level might contribute to the association between cognitive activity and reduced risk, any bias introduced by such factors is probably not strong enough to fully account for the observed association,” Deborah Blacker, MD, ScD, director of the Gerontology Research Unit in the Massachusetts General Hospital Department of Psychiatry, and senior author of the study, said in a statement.

The researchers used a database they maintain at the Harvard T.H. Chan School of Public Health on the Alzheimer’s Research Forum website cataloguing evidence from observational studies and some clinical trials about risk and protective factors for Alzheimer’s disease. The study authors, led by Gautam Sajeev, ScD, performed a systematic review of studies examining the impact of cognitive activity.

The research team analyzed 12 peer-reviewed studies that examined the relationship between late-in-life cognitive activities and the incidence of Alzheimer’s disease or other types of dementia. The studies included 13,939 individual participants and 1663 dementia cases, of which 565 were evaluated as Alzheimer’s disease. The data consistently showed a benefit for cognitive activity. The researchers also conducted a bias analysis that evaluated how much confounding factors, such as socioeconomic status or having depression, might influence reported associations between the amount of cognitive activity and the risk of dementia.

The study was unable to rule out the possibility that “reverse causation”—a reduction in cognitive activity among people already in a cognitive decline ahead of Alzheimer’s dementia—might have created an apparent causal relationship, the authors noted. Further study using clinical trials with long-term follow up is needed to better address this concern, they said.

However, based on their results, Blacker said cognitive activity appears to offer some modest protection, and she stressed that any impact will be relative and not absolute. She recommended being involved in any cognitive activities that are interesting and enjoyable because there is no evidence that one kind of activity is superior to another. More research is needed to confirm the findings and to find out the optimal type, duration, intensity, and timing of the cognitive activities.