Total Sedentary Time and Cognitive Function in Middle-Aged and Older Adults: A Systematic Review and Meta-analysis

Sedentary behavior and lifespan brain health

Higher levels of physical activity are known to benefit aspects of brain health across the lifespan. However, the role of sedentary behavior (SB) is less well understood. In this review we summarize and discuss evidence on the role of SB on brain health (including cognitive performance, structural or functional brain measures, and dementia risk) for different age groups, critically compare assessment approaches to capture SB, and offer insights into emerging opportunities to assess SB via digital technologies. Across the lifespan, specific characteristics of SB (particularly whether they are cognitively active or cognitively passive) potentially act as moderators influencing the associations between SB and specific brain health outcomes. We outline challenges and opportunities for future research aiming to provide more robust empirical evidence on these observations.

Multidomain interventions for sarcopenia and cognitive flexibility in older adults for promoting healthy aging: a systematic review and meta-analysis of randomized controlled trials

The global population is undergoing rapid aging, making physical activity a crucial element in preventing mortality and lowering the risk of Alzheimer's disease. Age-related declines in muscle mass and cognitive abilities significantly contribute to frailty and dependency. Thus, this study focuses on a meticulous analysis of the protective effects of multidomain interventions, an emerging resource combating age-related declines. It seeks to underscore their profound impact on cognitive flexibility and sarcopenia, highlighting their pivotal role in mitigating the adverse effects of aging. To identify relevant randomized controlled trials up to November 2023, we reviewed eight online academic databases, following PERSiST guidelines, PRISMA reporting system, and PICOs criteria. Meta-analyses on selected functional outcomes utilized a random-effects model, including the Timed Up and Go Test, Sit to Stand Test, Victoria Stroop Test, and Trail Making Test. Out of 2082 scrutinized articles, 17 were included in the systematic review, and 8 in the meta-analysis. Positive effects (p = 0.05, I2 = 57%; 95% CI - 0.63 to - 0.05) were observed in cognitive flexibility for certain interventions. Similarly, interventions addressing muscle strength demonstrated improvements in the Sit to Stand Test for the exercise group compared to the control group (p = 0.02, I2 = 0%; 95% CI - 0.63 to - 0.05). These findings underscore the importance of incorporating physical activity as a primary component of public health interventions for promoting healthy aging and reducing the burden of age-related diseases. Future interventions may explore more homogeneous approaches and evaluate the impact of thrice multidomain weekly sessions.

Cross-sectional and longitudinal neural predictors of physical activity and sedentary behaviour from a 6-month randomized controlled trial

A sedentary lifestyle offers immediate gratification, but at the expense of long-term health. It is thus critical to understand how the brain evaluates immediate rewards and long-term health effects in the context of deciding whether to engage in moderate-to-vigorous physical activity (MVPA) or sedentary behaviour (SB). In this secondary analysis of a 6-month randomized controlled trial to increase MVPA and reduce SB among community-dwelling adults, we explored how neural activity during an executive control task was associated with MVPA and SB levels. At baseline, a subset of participants (n = 26/61) underwent task-based functional magnetic resonance imaging (fMRI) to examine neural activity underlying executive control using the Now/Later task. MVPA and SB were measured objectively using the Sensewear Mini at baseline, and 2, 4, and 6 months follow-up. We then examined the associations of baseline neural activation underlying executive control with: (1) baseline MVPA or SB; and (2) changes in MVPA and SB over 6 months. Our results determined that there is a complex neurocognitive system associated with MVPA levels, while SB appears to lack any neurocognitive control. In other words, MVPA appears to require neurocognitive effort, while SB may be the default behavioural pattern in adults.

Variety and Duration of Different Sedentary Behaviors, Inflammation, Genetic Susceptibility, and New-Onset Dementia in the Older Population

OBJECTIVES

We aimed to evaluate the relationship of the variety and duration of different sedentary behaviors (TV-watching, driving, and nonoccupational computer use) with the risk of dementia in older participants, and examine whether inflammation and genetic susceptibility may modify the relationship.

DESIGN

A prospective cohort study.

SETTING AND PARTICIPANTS

173,829 older participants (≥60 years) without prior dementia in the UK Biobank were enrolled.

METHODS

A healthy sedentary behavior score was calculated as the number of the 3 major sedentary behaviors with a duration associated with the lowest risk of dementia. The primary outcome was new-onset all-cause dementia.

RESULTS

During a median follow-up of 12.4 years, 4965 (2.9%) participants developed new-onset dementia. There were U-shaped associations for TV-watching and driving time, and a reversed J-shaped association for nonoccupational computer use time with new-onset all-cause dementia, with the lowest dementia risk at >0-<2 hours/day for all the 3 sedentary behaviors. Moreover, a higher healthy sedentary behavior score was significantly associated with a lower risk of all-cause dementia (per 1 score increment: hazard ratio 0.78, 95% CI 0.75-0.81), with a stronger inverse association in those with higher levels of high-sensitivity C-reactive protein and monocytes (both P-interactions <.05). Genetic risks of dementia did not significantly modify the association. Similar trends were found for new-onset Alzheimer's disease and vascular dementia.

CONCLUSIONS AND IMPLICATIONS

The associations between the duration of different sedentary behaviors and new-onset dementia were different in the older population. Moreover, the variety of sedentary behavior was inversely associated with new-onset dementia, especially among those with higher levels of inflammation.

Purpose in life and accelerometer-measured physical activity among older adults

OBJECTIVE

Purpose in life is associated with engagement in physical activity and better cognitive health. This study examines the association between purpose in life and patterns of physical activity measured with an accelerometer and whether these patterns mediate the association between purpose and episodic memory among older adults.

METHODS AND MEASURES

This research is a secondary analysis of data from the accelerometry sub-study of the National Health and Aging Trends Study. Participants (N = 747; mean age = 79.20) reported on their purpose, wore an accelerometer for eight days, and completed an episodic memory task.

RESULTS

Purpose in life was associated with healthier patterns of physical activity, including higher total activity counts (β = .10, p = .002), more active bouts per day (β = .11, p = .003), less activity fragmentation (β = -.17, p < .001) and more sedentary fragmentation (β = .11, p = .002). These associations were generally similar across age, sex, race and education. Higher total activity counts and less activity fragmentation were associated with better episodic memory and accounted for part of the association between purpose and episodic memory.

CONCLUSION

Purpose in life is associated with healthier patterns of physical activity measured through accelerometry among older adults and such patterns may be one factor in the pathway from purpose to healthier episodic memory.

Accelerometer-Measured Sedentary Behavior Patterns, Brain Structure, and Cognitive Function in Dementia-Free Older Adults: A Population-Based Study

BACKGROUND

Sedentary behavior is associated with cognitive impairment, but the neuropathological mechanisms underlying their associations are poorly understood.

OBJECTIVE

To investigate the associations of accelerometer-measured sedentary behavior patterns with brain structure and cognition, and further to explore the potential mechanisms.

METHODS

This community-based study included 2,019 older adults (age≥60 years, 59% women) without dementia derived from participants in the baseline examination of MIND-China (2018-2020). We assessed sedentary parameters using an accelerometer and cognitive function using a neuropsychological test battery. Structural brain markers were assessed on the structural brain MRI scans in a subsample (n = 1,009). Data were analyzed using the general linear, isotemporal substitution, and mediation models.

RESULTS

In the total sample (n = 2,019), adjusting for multiple covariates and moderate-to-vigorous-intensity physical activity, longer mean sedentary bout duration was linearly related with lower z-scores of global cognition, verbal fluency, and memory (ptrend < 0.05), whereas greater total sedentary time was linearly associated with lower z-scores of global cognition, verbal fluency, and memory only among individuals with long sedentary time (>10 h/day) (ptrend < 0.05); Breaking up sedentary time with same amount of light-intensity physical activity was significantly associated with higher verbal fluency and memory z-scores (p < 0.05). In the MRI subsample (n = 1,009), separately entering structural brain MRI markers into the mediation models substantially attenuated the associations of mean sedentary bout duration with global cognition, verbal fluency, and memory z-scores.

CONCLUSION

Prolonged uninterrupted sedentary time is associated with poor global cognition, memory, and verbal fluency among rural older adults, and structural brain markers could partially mediate the association.