Physical activity and amyloid beta in middle-aged and older adults: A systematic review and meta-analysis

BACKGROUND

One of the pathological hallmarks distinguishing Alzheimer's disease from other dementias is the accumulation of amyloid beta (Aβ). Higher physical activity is associated with decreased dementia risk, and one potential path could be through Aβ levels modulation. We aimed to explore the relationship between physical activity and Aβ in middle-aged and older adults.

METHODS

A systematic search of PubMed, Web of Science, PsycINFO, Cochrane Central Register of Controlled Trials, and SPORTDiscus was performed from inception to April 28, 2022. Studies were eligible if they included physical activity and Aβ data in adults aged 45 years or older. Multi-level meta-analyses of intervention and observational studies were performed to examine the role of physical activity in modulating Aβ levels.

RESULTS

In total, 37 articles were included (8 randomized controlled trials, 3 non-randomized controlled trials, 4 prospective longitudinal studies, and 22 cross-sectional studies). The overall effect size of physical activity interventions on changes in blood Aβ was medium (pooled standardized mean difference = -0.69, 95% confidence interval (95%CI): -1.41 to 0.03; I2 = 74.6%). However, these results were not statistically significant, and there were not enough studies to explore the effects of physical activity on cerebrospinal fluid (CSF) and brain Aβ. Data from observational studies were examined based on measurements of Aβ in the brain using positron emission tomography scans, CSF, and blood. Higher physical activity was positively associated with Aβ only in the CSF (Estimate r = 0.12; 95%CI: 0.05-0.18; I2 = 38.00%).

CONCLUSION

Physical activity might moderately reduce blood Aβ in middle-aged and older adults. However, results were only near statistical significance and might be interpreted with caution given the methodological limitations observed in some of the included studies. In observational studies, higher levels of physical activity were positively associated with Aβ only in CSF. Therefore, further research is needed to understand the modulating role of physical activity in the brain, CSF, and blood Aβ, as well as its implication for cognitive health.

Physical Performance and Amyloid-β in Humans: A Systematic Review and Meta-Analysis of Observational Studies

BACKGROUND

Accumulation of amyloid-β (Aβ) plaques is one of the main features of Alzheimer's disease (AD). Physical performance has been related to dementia risk and Aβ, and it has been hypothesized as one of the mechanisms leading to greater accumulation of Aβ. Yet, no evidence synthesis has been performed in humans.

OBJECTIVE

To investigate the association of physical performance with Aβ in humans, including Aβ accumulation on brain, and Aβ abnormalities measured in cerebrospinal fluid (CSF) and blood.

METHODS

A systematic review with multilevel meta-analysis was performed from inception to June 16th, 2022. Studies were eligible if they examined the association of physical performance with Aβ levels, including the measure of physical performance as a predictor and the measure of Aβ as an outcome in humans.

RESULTS

7 articles including 2,619 participants were included in the meta-analysis. The results showed that physical performance was not associated with accumulation of Aβ in the brain (ES = 0.01; 95% CI -0.21 to 0.24; I2 = 69.9%), in the CSF (ES = -0.28; 95% CI -0.98 to 0.41; I2 = 91.0%) or in the blood (ES = -0.19; 95% CI -0.61 to 0.24; I2 = 99.75%). Significant heterogeneity was found across the results , which posed challenges in arriving at consistent conclusions; and the limited number of studies hindered the opportunity to conduct a moderation analysis.

CONCLUSIONS

The association between physical performance and Aβ is inconclusive. This uncertainly arises from the limited number of studies, study design limitations, and heterogeneity of measurement approaches. More studies are needed to determine whether physical performance is related to Aβ levels in humans.