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

Comments

  1. This study by Floud et al. is a very nice and large study including over 800,000 women followed for approximately 16 years. The women were aged approximately 60 years when information on social and cognitive activity was collected. The social and cognitive activities were adult education, engagement in group activities including art, craft, or music, and engaging in voluntary work. They found that the protective effect of social and cognitive activity on risk of dementia was especially strong during the first four years of follow-up and that the effect diminished during the second decade. This has also been shown for physical activity in a recent report based on the same population and with similar methods.

    As the authors state, these results show that engagement in leisure-time activity declines due to preclinical dementia. The authors also conclude that leisure-time activity has no causal relation to dementia risk. However, although evidence suggest that engagement in leisure-time activities declines in the years preceding dementia onset, leisure-time activities may still have a causal relation with dementia risk. One need not exclude the other.

    This is supported by findings from studies with observation periods over four decades (e.g., Carlson et al., 2008; Najar et al., 2019; Hörder et al., 2018). In our 2019 study, we found that midlife leisure-time cognitive activity reduced risk of all-cause dementia and Alzheimer’s disease after 44 years of follow-up, while midlife physical activity was associated with reduced risk of mixed vascular dementia disorders. Also, to minimize the risk of preclinical dementia affecting our results, we performed sensitivity analyses excluding those with dementia within 22 years of follow-up. The results remained similar, if not a little bit stronger for at least physical activity, which then also associated with all-cause dementia.

    There are of course several methodological differences between these two studies that could explain the divergent results. For example, the women included in our study were younger at baseline (mean age 47 years), assessment of dementia differed between the studies (we used the DSM-III-R criteria, which are based on neuropsychiatric examinations, while Floud and colleagues used electronic health records), and we had a longer follow-up period.

    In conclusion, this work highlights an important aspect in studies examining risk factors for dementia, namely the risk of reverse causation due to preclinical dementia. 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.

    References:

    . Midlife activity predicts risk of dementia in older male twin pairs. Alzheimers Dement. 2008 Sep 1;4(5):324-31. PubMed.

    . Cognitive and physical activity and dementia: A 44-year longitudinal population study of women. Neurology. 2019 Mar 19;92(12):e1322-e1330. Epub 2019 Feb 20 PubMed.

    . Midlife cardiovascular fitness and dementia: A 44-year longitudinal population study in women. Neurology. 2018 Apr 10;90(15):e1298-e1305. Epub 2018 Mar 14 PubMed.

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References

News Citations

  1. Late-Life Brain Workouts May Hold Off Dementia, Meta-Analysis Concludes

Paper Citations

  1. . Social activity, cognitive decline and dementia risk: a 20-year prospective cohort study. BMC Public Health. 2015 Oct 24;15:1089. PubMed.
  2. . Cognitive and physical activity and dementia: A 44-year longitudinal population study of women. Neurology. 2019 Mar 19;92(12):e1322-e1330. Epub 2019 Feb 20 PubMed.
  3. . Leisure Activity in Old Age and Risk of Dementia: A 15-Year Prospective Study. J Gerontol B Psychol Sci Soc Sci. 2013 Jun 13; PubMed.

Further Reading

Papers

  1. . Lack of associations between modifiable risk factors and dementia in the very old: findings from the Cambridge City over-75s cohort study. Aging Ment Health. 2017 Feb 2;:1-7. PubMed.
  2. . Community engagement and dementia risk: time-to-event analyses from a national cohort study. J Epidemiol Community Health. 2020 Jan;74(1):71-77. Epub 2019 Oct 29 PubMed.

Primary Papers

  1. . Cognitive and social activities and long-term dementia risk: the prospective UK Million Women Study. Lancet Public Health. 2021 Feb;6(2):e116-e123. PubMed.