Association of Physical Activity with Incidence of Dementia Is Attenuated by Air Pollution

Exploring the Interplay Between Climate Change, 24-Hour Movement Behavior, and Health: A Systematic Review

BACKGROUND

Given the emergence of climate change and health risks, this review examined potential relationships between varying indicators of climate change, movement behaviors (ie, physical activity [PA], sedentary behavior, and sleep), and health.

METHODS

Seven databases were searched in March 2020, April 2023, and April 2024. To be included, studies must have examined indicators of climate change and at least one of the movement behaviors as either an exposure or a third variable (ie, mediator/moderator), and a measure of health as outcome. Evidence was summarized by the role (mediator/moderator) that either climate change or movement behavior(s) has with health measures. Relationships and directionality of each association, as well as the strength and certainty of evidence were synthesized.

RESULTS

A total of 79 studies were eligible, representing 6,671,791 participants and 3137 counties from 25 countries (40% low- and middle-income countries). Of 98 observations from 17 studies that examined PA as a mediator, 34.7% indicated that PA mediated the relationship between climate change and health measure such that indicators of adverse climate change were associated with lower PA, and worse health outcome. Of 274 observations made from 46 studies, 28% showed that PA favorably modified the negative association between climate change and health outcome. Evidence was largely lacking and inconclusive for sedentary behavior and sleep, as well as climate change indicators as an intermediatory variable.

CONCLUSIONS

PA may mitigate the adverse impact of climate change on health. Further evidence is needed to integrate PA into climate change mitigation, adaptation, and resilience strategies.

The interaction between physical activity and ambient particulate matters on cognitive function among Chinese community-dwelling older adults

BACKGROUND

The interaction between physical activity (PA) and ambient particulate matters (PMs) on cognition is rarely investigated. Our study aimed to assess the interactions of PA and PMs on cognitive function in older adults.

METHODS

Our study comprised 3937 Chinese community-dwelling older adults. Cognition was evaluated using the Mini-Mental State Examination. PA information was gathered using the International Physical Activity Questionnaire. The data of PMs were obtained from China High Air Pollutants (CHAP). Linear regressions model and interaction plots were applied to assess and visualize the interaction of PA and PMs on cognition, respectively. Bayesian kernel machine regression (BKMR) method was employed to visualize discernible thresholds for the interaction.

RESULTS

PMs were negatively associated with MMSE scores (PM1: β = -0.40, 95 % CI: -0.58, -0.28; PM2.5: β = -0.46, 95 % CI: -0.64, -0.29; PM10: β = -0.44, 95 % CI: -0.61, -0.26), and PA was positively affiliated with MMSE scores (β = 0.18, 95 % CI: -0.01, 0.38). Interaction plots and BKMR demonstrated that adverse connotations of PMs with MMSE increased with the elevated PA levels, and the positive associations of PA with MMSE scores were attenuated by increased PMs (all Pinteraction < 0.20). Discernible thresholds for the interaction between PMs and PA on MMSE were found.

CONCLUSIONS

Our findings suggest that PA should not be taken at higher PMs concentrations, and that low level of PA could be performed in PMs polluted environment to improve cognitive function. Further experimental and cohort researches are required to reproduce our discovery.

Air Pollution as an Environmental Risk Factor for Alzheimer's Disease and Related Dementias

Alzheimer's disease and related dementias are a leading cause of morbidity in our aging populations. Although influenced by genetic factors, fewer than 5% of Alzheimer's disease and related dementia cases are due solely to genetic causes. There is growing scientific consensus that these dementias arise from complex gene by environment interactions. The 2020 Lancet Commission on dementia prevention, intervention, and care identified 12 modifiable risk factors of dementia, including lifestyle, educational background, comorbidities, and environmental exposures to environmental contaminants. In this review, we summarize the current understanding and data gaps regarding the role(s) of environmental pollutants in the etiology of Alzheimer's disease and related dementias with a focus on air pollution. In addition to summarizing findings from epidemiological and experimental animal studies that link airborne exposures to environmental contaminants to increased risk and/or severity of Alzheimer's disease and related dementias, we discuss currently hypothesized mechanism(s) underlying these associations, including peripheral inflammation, neuroinflammation and epigenetic changes. Key data gaps in this rapidly expanding investigative field and approaches for addressing these gaps are also addressed.

Long-term exposure to air pollution and road traffic noise and incidence of dementia in the Danish Nurse Cohort

INTRODUCTION

We examined the association of long-term exposure to air pollution and road traffic noise with dementia incidence in the Danish Nurse Cohort.

METHODS

Female nurses were followed for dementia incidence (hospital contact or medication prescription) from 1993/1999 to 2020. Air pollution and road traffic noise levels were estimated at nurses' residences, and their associations with dementia were examined using Cox regression models.

RESULTS

Of 25,233 nurses 1409 developed dementia. Particulate matter with a diameter of ≤2.5 µm (PM2.5) was associated with dementia incidence, after adjusting for lifestyle, socioeconomic status, and road traffic noise (hazard ratio [95% confidence interval] 1.35 [1.15-1.59] per interquartile range of 2.6 µg/m3). There was no association of PM2.5 with dementia in physically active nurses. Association with road traffic noise diminished after adjusting for PM₂.₅ (1.02 [0.93-1.11] per 7.6 dB).

DISCUSSION

Long-term exposure to air pollution increases risk of dementia, and physical activity may moderate this risk.

HIGHLIGHTS

Long-term exposure to air pollution was associated with increased risk of dementia among female nurses from the Danish Nurse Cohort. Association of air pollution with dementia was independent of road traffic noise. Association of road traffic noise with dementia diminished after adjusting for air pollution. Physical activity moderated adverse effects of air pollution on dementia.

Physiological impacts of atmospheric pollution: Effects of environmental air pollution on exercise

In this review, we discuss some of the recent advances in our understanding of the physiology of the air pollution and exercise. The key areas covered include the effect of exercise intensity, the effects of pre-exposure to air pollution, acclimation to air pollution, and the utility of masks during exercise. Although higher intensity exercise leads to an increase in the inhaled dose of pollutants for a given distance traveled, the acute effects of (diesel exhaust) air pollution do not appear to be more pronounced. Second, exposure to air pollution outside of exercise bouts seems to have an effect on exercise response, although little research has examined this relationship. Third, humans appear to have an ability to acclimate to ground level ozone, but not other pollutants. And finally, masks may have beneficial effects on certain outcomes at low intensity exercise in pollution with significant levels of particles, but more study is required in realistic conditions.

Leisure-Time Physical Activity May Attenuate the Impact of Diabetes on Cognitive Decline in Middle-Aged and Older Adults: Findings From the ELSA-Brasil Study

OBJECTIVE

To assess leisure-time physical activity (LTPA) as a modifier of the diabetes/cognitive decline association in middle-aged and older participants in the Estudo Longitudinal de Saude do Adulto (ELSA-Brasil) study.

RESEARCH DESIGN AND METHODS

ELSA-Brasil is a cohort of 15,105 participants (age 35-74 years) enrolled between 2008 and 2010. We evaluated global cognitive function, summing the scores of six standardized tests evaluating memory and verbal fluency, including the Trail-Making Test, at baseline and follow-up. Incident cognitive impairment was defined as a global cognitive function score at follow-up lower than -1 SD from baseline mean. Participants reporting ≥150 min/week of moderate to vigorous LTPA at baseline were classified as physically active. We assessed the association of LTPA with global cognition change in those with diabetes in the context of our overall sample through multivariable regression models.

RESULTS

Participants' (N = 12,214) mean age at baseline was 51.4 (SD 8.8) years, and 55.5% were women. During a mean follow-up of 8.1 (SD 0.6) years, 9,345 (76.5%) inactive participants and 1,731 (14.1%) participants with diabetes at baseline experienced faster declines in global cognition than those who were active (β = -0.003, -0.004, and -0.002) and those without diabetes (β = -0.004, -0.005, and -0.003), respectively. Diabetes increased the risk of cognitive impairment (hazard ratio [HR] 1.71; 95% Cl 1.22, 2.39) in inactive but not in active adults (HR 1.18; 95% CI 0.73, 1.90). Among participants with diabetes, those who were active showed a delay of 2.73 (95% CI 0.94, 4.51) years in the onset of cognitive impairment.

CONCLUSIONS

In adults living with diabetes, LTPA attenuated the deleterious association between diabetes and cognitive function.

The joint effect and hemodynamic mechanism of PA and PM2.5 exposure on cognitive function: A randomized controlled trial study

BACKGROUND

While PM2.5 has been shown to impair cognitive function, physical activity (PA) is known to enhance it. Nonetheless, considering the increased inhalation of PM2.5 during exercise, the potential of PA to counteract the detrimental effects of PM2.5, along with the underlying hemodynamic mechanisms, remains uncertain.

METHODS

We conducted a double-blinded, randomized controlled trial among healthy young adults in Beijing, China. Ninety-three participants were randomly allocated to groups experiencing different intensities of PA interventions, and either subjected to purified or unpurified air conditions. Cognitive function was measured by the Color-Word Matching Stroop task, and the hemodynamic response was measured using functional near-infrared spectroscopy during participants performed the Stroop task both before and after the intervention. Linear mixed-effect models were used to estimate the impact of PA and PM2.5 on cognitive function and hemodynamic response.

RESULTS

The reaction time for congruent and incongruent Stroop tasks improved by - 80.714 (95% CI: -136.733, -24.695) and - 105.843 (95% CI: -188.6, -23.085) milliseconds after high-intensity interval training (HIIT) intervention. PM2.5 and HIIT had interaction effects on cognition, such that every 1 μg/m3 increase in PM2.5 attenuated the benefits of HIIT on reaction time by 2.231 (95% CI: 0.523, 3.938) and 3.305 (95% CI: 0.791, 5.819) milliseconds for congruent and incongruent Stroop tasks. Moreover, we divided participants into high and low PM2.5 exposure groups based on average PM2.5 concentration (32.980 μg/m3), and found that HIIT intervention in high PM2.5 concentration led to 69.897 (95% CI: 9.317, 130.476) and 99.269 (95% CI: 10.054, 188.485) milliseconds increased in the reaction time of congruent and incongruent Stroop, compared with the control group among low PM2.5. Furthermore, we found a significant interaction effects of PM2.5 and moderate-intensity continuous training (MICT) on the middle frontal gyrus (MFG) and dorsolateral superior frontal gyrus (DLPFC). PM2.5 and HIIT had a significant interaction effect on the DLPFC.

CONCLUSIONS

HIIT improved cognitive function, but the cognitive benefits of HIIT were attenuated or even reversed under high PM2.5 exposure. The activation of the DLPFC and MFG could serve as hemodynamic mechanisms to explain the joint effect of PA and PM2.5.

Leisure-time physical activity mitigated the cognitive effect of PM2.5 and PM2.5 components exposure: Evidence from a nationwide longitudinal study

BACKGROUND

Exposure to fine particulate matter (PM2.5) impairs cognition, while physical activity (PA) improves cognitive function. However, whether taking PA with PM2.5 exposure is still beneficial to cognition remains unknown.

METHODS

We utilized national representative longitudinal data from the China Family Panel Study (CFPS), comprising a total sample of 108,099 from 2010 to 2018 in three waves. Cognitive performance and leisure-time PA were measured using the standard cognitive module and Godin-Shephard Leisure-Time Physical Activity Questionnaire. Gridded overall PM2.5 and major chemical components of PM2.5 were estimated using a two-stage machine learning model and matched to each participant based on their residential location. Mixed-effect models and difference-in-difference models were employed to investigate the individual and joint effects of total PM2.5, PM2.5 components, and leisure-time PA on cognition.

RESULTS

Every 1 μg/m3 increase in PM2.5 was associated with a -0.035 (95% confidence interval [CI] = -0.052, -0.018) point change in cognitive score. All PM2.5 components exhibited negative associations with cognitive change, with black carbon (BC) contributing the most significant cognitive decline (β = -1.025, 95% CI = -1.367, -0.683). Every one-time (or one-hour) increase in leisure-time PA frequency (or PA time) per week was associated with an increase in cognitive score by 0.576 (0.270) points (PA frequency: 95% CI = 0.544, 0.608, PA time: 95% CI = 0.248, 0.293). PA frequency (β = -0.005, 95% CI = -0.006, -0.003) and PA time (β = -0.002, 95% CI = -0.003, -0.001) exhibited interactive effects with PM2.5. Increased PA frequency and time were more beneficial to cognitive function in the low PM2.5 exposure group compared to those exposed to high PM2.5 levels. Moreover, relative to lower PM2.5 exposure, the cognitive benefits of physically active individuals with higher PM2.5 exposure were attenuated but still improved cognition when compared to those with no PA.

CONCLUSION

Engaging in leisure-time PA provides cognitive benefits even under PM2.5 exposure, although PM2.5 exposure attenuates these benefits. Among all PM2.5 components, BC demonstrated the most significant cognitive hazard and interaction with leisure-time PA. Promoting PA as a preventive measure may offer a cost-effective and convenient strategy to mitigate the negative impact of PM2.5 exposure on cognition. There is no excuse to avoid PA under PM2.5 exposure, as its cognitive benefits persist even in polluted environments.

Ambient air pollution and clinical dementia: systematic review and meta-analysis

OBJECTIVE

To investigate the role of air pollutants in risk of dementia, considering differences by study factors that could influence findings.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

EMBASE, PubMed, Web of Science, Psycinfo, and OVID Medline from database inception through July 2022.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Studies that included adults (≥18 years), a longitudinal follow-up, considered US Environmental Protection Agency criteria air pollutants and proxies of traffic pollution, averaged exposure over a year or more, and reported associations between ambient pollutants and clinical dementia. Two authors independently extracted data using a predefined data extraction form and assessed risk of bias using the Risk of Bias In Non-randomised Studies of Exposures (ROBINS-E) tool. A meta-analysis with Knapp-Hartung standard errors was done when at least three studies for a given pollutant used comparable approaches.

RESULTS

2080 records identified 51 studies for inclusion. Most studies were at high risk of bias, although in many cases bias was towards the null. 14 studies could be meta-analysed for particulate matter <2.5 µm in diameter (PM2.5). The overall hazard ratio per 2 μg/m3 PM2.5 was 1.04 (95% confidence interval 0.99 to 1.09). The hazard ratio among seven studies that used active case ascertainment was 1.42 (1.00 to 2.02) and among seven studies that used passive case ascertainment was 1.03 (0.98 to 1.07). The overall hazard ratio per 10 μg/m3 nitrogen dioxide was 1.02 ((0.98 to 1.06); nine studies) and per 10 μg/m3 nitrogen oxide was 1.05 ((0.98 to 1.13); five studies). Ozone had no clear association with dementia (hazard ratio per 5 μg/m3 was 1.00 (0.98 to 1.05); four studies).

CONCLUSION

PM2.5 might be a risk factor for dementia, as well as nitrogen dioxide and nitrogen oxide, although with more limited data. The meta-analysed hazard ratios are subject to limitations that require interpretation with caution. Outcome ascertainment approaches differ across studies and each exposure assessment approach likely is only a proxy for causally relevant exposure in relation to clinical dementia outcomes. Studies that evaluate critical periods of exposure and pollutants other than PM2.5, and studies that actively assess all participants for outcomes are needed. Nonetheless, our results can provide current best estimates for use in burden of disease and regulatory setting efforts.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42021277083.

Global ambient particulate matter pollution and neurodegenerative disorders: a systematic review of literature and meta-analysis

Previous studies on particulate matter (PM) exposure and neurodegenerative disorders showed inconsistent results, and few studies systematically examined the long-term effect of PM on neurodegenerative diseases, including all-cause dementia, Alzheimer's disease, Parkinson's disease, vascular dementia, amyotrophic lateral sclerosis, and cognitive function decline. We systematically searched for published studies in PubMed, Embase, Cochrane Library, and Web of Science up to October 31, 2022. To facilitate a comparison of effect sizes from different studies, we standardized units across studies to a 10 μg/m³ increase for PM. Heterogeneity was assessed by Cochran's Q test and I² statistic. Publication bias was evaluated using funnel plots and Egger's tests. Subgroup analysis, meta-regression, and sensitivity analysis were performed. The protocol for this review was registered with PROSPERO (CRD42021277112). Of the 3403 originally identified studies, a meta-analysis was finally performed in 49 studies. The results showed that there was a significant positive association between long-term PM_2.5 exposure and all-cause dementia, Alzheimer's disease as well as Parkinson's disease, with pooled OR of 1.30 (95%CI: 1.14, 1.47, I² = 99.3%), 1.65 (95%CI: 1.37, 1.94, I² = 98.2%), and 1.17 (95%CI: 1.00, 1.33, I² = 91.8%). A positive association between PM₁₀ and vascular dementia was observed (OR = 1.12, 95%CI: 1.04, 1.21, I² = 0.0%). Association between PM exposure and decreased cognitive function score was found. Our results highlight the important role of PM pollution, particularly PM_2.5, in the risk of age-related neurodegenerative diseases and cognitive function decline.

Leisure-time sedentary behaviors are differentially associated with all-cause dementia regardless of engagement in physical activity

Sedentary behavior (SB) is associated with cardiometabolic disease and mortality, but its association with dementia is currently unclear. This study investigates whether SB is associated with incident dementia regardless of engagement in physical activity (PA). A total of 146,651 participants from the UK Biobank who were 60 years or older and did not have a diagnosis of dementia (mean [SD] age: 64.59 [2.84] years) were included. Self-reported leisure-time SBs were divided into two domains: time spent watching television (TV) or time spent using a computer. A total of 3,507 individuals were diagnosed with all-cause dementia over a mean follow-up of 11.87 (±1.17) years. In models adjusted for a wide range of covariates, including time spent in PA, time spent watching TV was associated with increased risk of incident dementia (HR [95% CI] = 1.24 [1.15 to 1.32]) and time spent using a computer was associated with decreased risk of incident dementia (HR [95% CI] = 0.85 [0.81 to 0.90]). In joint associations with PA, TV time and computer time remained significantly associated with dementia risk at all PA levels. Reducing time spent in cognitively passive SB (i.e., TV time) and increasing time spent in cognitively active SB (i.e., computer time) may be effective behavioral modification targets for reducing risk of dementia regardless of engagement in PA.