Keeping the brain active in our golden years—whether by taking up a hobby, doing those crossword puzzles, or socializing with friends—can stave off dementia, right? While this “use it or lose it” mantra seems intuitive, it might not be true, according to a study published in the February issue of Lancet Public Health. Tapping extensive longitudinal data from more than 850,000 women, researchers led by Sarah Floud at the University of Oxford in England found that women who reported not participating in enriching activities were more likely to develop dementia within the following few years. Ten years later, however, the inactive women were no more likely to get dementia than those who had reported being active. The findings suggest that not partaking in brain-stimulating activities is a symptom of, rather than causes, incipient dementia.
- 850,000 healthy women were tracked for incident dementia for 16 years.
- Inactivity correlated with dementia onset within the first five years.
- Inactivity did not correlate with dementia onset more than a decade later.
- Findings cast sedentary lifestyle as part of dementia prodrome.
“This study highlights an important aspect in studies examining risk factors for dementia, which is the risk of reverse causation due to preclinical dementia,” wrote Jenna Najar of the University of Gothenburg, Sweden, to Alzforum. “Therefore, studies with observation periods longer than the assumed preclinical phase of dementia (>20–30 years) are needed to better understand causal relations between lifestyle factors and risk of dementia.”
Multiple studies have demonstrated that several years before a dementia diagnosis, people tend to engage less and less in activities that stretch the mind and keep them socially engaged. This has led to recommendations by public health agencies for older people to engage in such activities to prevent dementia. However, the gradual, decades-long accumulation of brain pathology that precedes dementia means that avoidance of these activities could be an early symptom of, rather than a contributor to, ongoing neurodegeneration (Aug 2016 news).
Exceedingly long follow-up studies—on par with the duration of the preclinical phase of neurodegenerative disease—are needed to settle the question. However, few longitudinal studies have follow-up periods lasting more than a decade, and even fewer compare short-term and long-term associations between lifestyle and dementia (Marioni et al., 2015; Najar et al., 2019; Sörman et al., 2013).
Floud and colleagues turned to the massive U.K. Million Woman Study to investigate. For this prospective study, the country’s National Health Service invited more than one million women for breast cancer screening in 1998. At a follow-up visit in 2001, women were asked how much they engaged in adult education, arts, crafts, music groups, and volunteer work. In 2006, they answered questions about reading. Then, their electronic health records were monitored for the first mention of dementia in a hospital record. All told, more than 850,000 women responded in 2001, when they averaged 60 years of age. A decade later, only 1 percent had died or emigrated out of the U.K.
Participants were tracked for an average of 16 years, during which time 90 percent of them were admitted to the hospital at least once. Dementia was mentioned in hospital records for 4 percent, or 31,187 women. Of these dementia cases, only 3 percent, or 848, were detected during the first five years of follow-up, while 15 percent, or 4,703, were detected between five and nine years, and 82 percent, or 25,636, cropped up in the second decade.
The effect wasn’t small. Lack of participation in adult education, arts, crafts, music, or volunteer work nearly doubled a woman’s chances of dementia in the first five years of follow-up. Alas, the association dropped sharply between five and nine years and was nonexistent after 10 years. A similar trend emerged for reading, although follow-up only lasted for an average of 12 years after the women had reported on that activity. Compared to bookworms, nonreaders had more than triple the chance of developing dementia within five years. This higher risk dropped to 1.37 between five and nine years, and to 1.13 after 10 years.
In all, the findings suggest that while lack of engagement in leisure activities does associate with dementia, it does so only during those years when brain pathology is likely already substantial, suggesting that avoiding stimulating activity is a symptom, not a cause, of the pathogenic process that leads to dementia.
Najar countered that although evidence shows engagement in leisure-time activities to decline in the years preceding dementia onset, this does not rule out that such activities may still have a causal relation with dementia risk. For example, Najar’s study reported that midlife leisure-time cognitive activity was associated with lower risk of all-cause dementia and Alzheimer’s disease after 44 years of follow-up (Najar et al., 2019). Najar thinks methodological differences, including the longer follow-up, younger baseline cohort, and ascertainment of dementia diagnosis, could explain the different results.
Yaakov Stern of Columbia University in New York commented that the study demonstrates how the dementing process—i.e., neuropathology such as Aβ and tau accumulation—can limit a person’s ability to take part in activities. However, he noted that the analysis only considered whether participants took part in an activity or not, rather than including their level of involvement in each specific activity, or their combined level of participation across multiple activities. He said that the findings leave open the possibility that those who are most engaged may enjoy some protection from dementia further down the road.—Jessica Shugart
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