People who regularly flex their thinking muscles in old age may have an edge up on cognitive couch potatoes when it comes to protection against dementia. That is the main conclusion of a meta-analysis that investigated the effect of late-life cognitive activity on the incidence of dementia and/or Alzheimer’s disease (AD). As reported in the September issue of Epidemiology, researchers led by Deborah Blacker at Harvard University scrutinized data from 12 observational studies. Even in the face of hefty confounders—including education level, socioeconomic status, and incipient dementia itself—keeping up mental exercise in old age appeared to genuinely stave off the symptoms of neurodegenerative disease. The meta-analysis results are on display in the AlzRisk database.
Findings from numerous studies have supported the “use it or lose it” mantra in regard to maintaining mental prowess into old age (see Verghese et al., 2003; Wilson et al., 2007; Akbaraly et al., 2009). However, the waters of this seemingly simple tenet are muddied by variations in how and when each study measured cognitive stimulation or treated a bevy of imposing confounders (see Jun 2014 news). What’s more, results of intervention trials have been mixed or difficult to interpret (see Jun 2014 news), and the FDA recently fined Lumos Labs, the creators of Lumosity “brain-training” programs, for hyping their product (see Jan 2016 news).
Given the increasing popularity of brain-training programs claiming to boost cognition (and maybe even prevent AD), Blacker told Alzforum that it was time to take stock of epidemiological studies conducted thus far. First author Gautam Sajeev and colleagues set out not only to compare the main conclusions of studies in the field, but also to estimate how much of their results could be explained by confounding variables that correlate with cognitive engagement, including education and socioeconomic status.
Out of 926 citations that popped up on their first database search, the researchers settled on 12 that met all their criteria for investigations that assessed the effect of late-life cognitive activity on the incidence of AD and/or all-cause dementia. The studies included data on nearly 14,000 participants in 11 cohorts. Ten prospective studies assessed baseline participation in cognitive activities late in life, and then followed the participants for 2.5 to six years to check for dementia. The other two were case-control studies, which also assessed cognitive activity in early to mid-life. Together, the investigations considered the number and/or frequency of multiple “cognitive” leisure activities, including reading books, playing cards, doing crossword puzzles, playing musical instruments, and even watching television. All found an inverse correlation between either the frequency or number of these activities and the incidence of AD or dementia.
The studies seemed to agree that cognitive engagement correlated with lower rates of dementia, but even so, how much of those results could be due to more schooling, higher socioeconomic status, and better cardiovascular health enjoyed by those who tend to regularly engage in cognitive activities? To get at this, the researchers conducted a bias analysis, in which they estimated how strongly each confounding variable might influence results. They concluded that while confounders would likely diminish the effect somewhat, they were unlikely to completely account for it.
The researchers were less sure about the potential contribution of reverse causation. This is the idea that early cognitive struggles that precede dementia for a number of years might discourage people from engaging in cognitive activities. Observational cohort studies using more sensitive cognitive measures are beginning to pick up subtle cognitive decrements a decade or more before a dementia diagnosis is made (e.g., Aug 2016 conference news). This implies that a person who gets a dementia diagnosis within five years of a baseline activity measurement likely had a cognitive impairment of some kind at baseline, even if it was not formally documented. The fact that most studies in this meta-analysis measured cognitive activity late in life and then tracked participants for relatively short periods of time makes this variable particularly challenging to control for, Blacker agreed. However, the researchers still concluded that the benefits of flexing those mental muscles were unlikely to be totally explained by reverse causation.
All in all, Blacker said the meta-analysis diminished some of her skepticism about the benefits of cognitive activities. No single pursuit or hobby has been proven to ward off dementia more than others; rather, it may be the depth of engagement that is important, she proposed. Therefore, Blacker remains skeptical of brain-training programs that claim to boost cognition, except for people who truly enjoy playing the games.—Jessica Shugart
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- Verghese J, Lipton RB, Katz MJ, Hall CB, Derby CA, Kuslansky G, Ambrose AF, Sliwinski M, Buschke H. Leisure activities and the risk of dementia in the elderly. N Engl J Med. 2003 Jun 19;348(25):2508-16. PubMed.
- Wilson RS, Scherr PA, Schneider JA, Tang Y, Bennett DA. Relation of cognitive activity to risk of developing Alzheimer disease. Neurology. 2007 Nov 13;69(20):1911-20. PubMed.
- Akbaraly TN, Portet F, Fustinoni S, Dartigues JF, Artero S, Rouaud O, Touchon J, Ritchie K, Berr C. Leisure activities and the risk of dementia in the elderly: results from the Three-City Study. Neurology. 2009 Sep 15;73(11):854-61. PubMed.
- Sajeev G, Weuve J, Jackson JW, VanderWeele TJ, Bennett DA, Grodstein F, Blacker D. Late-life Cognitive Activity and Dementia: A Systematic Review and Bias Analysis. Epidemiology. 2016 Sep;27(5):732-42. PubMed.