Associations of Air Pollution and Genetic Risk With Incident Dementia: A Prospective Cohort Study

Long-Term Exposure to PM2.5 Constituents, Genetic Susceptibility, and Incident Dementia: A Prospective Cohort Study among 0.2 Million Older Adults

Fine particulate matter, known as PM2.5, is recognized as a risk factor for dementia. However, the specific linkage between PM2.5 constituents and dementia is not well understood. We conducted a cohort of 217,336 participants of the UK Biobank to explore the association of long-term exposure to PM2.5 constituents with all-cause dementia, Alzheimer's disease (AD), and vascular dementia. We estimated PM2.5 constituents based on residential addresses by an evaluation model and used time-varying Cox models and Quantile g-computation models to assess the effects of individual constituents and their mixtures. Genetic susceptibility to dementia was assessed using a polygenic risk score, and its multiplicative and additive interactions with PM2.5 constituents were analyzed. Our results showed that black carbon (BC), ammonium (NH4+), organic matter (OM), and sulfate (SO42-) were positively associated with all-cause dementia, while BC and OM were linked to AD, with BC being the most influential. The combined effect of PM2.5 constituents and genetic risk was stronger than their individual effect. This study offers new insights into the association between PM2.5 constituents and dementia, especially those from fuel combustion and automobile exhaust, and highlights the need for effective prevention strategies.

Ambient Air Pollution and Parkinson's Disease and Alzheimer's Disease: An Updated Meta-Analysis

BACKGROUND

Previous epidemiological evidence regarding the associations between ambient air pollution and two major neurodegenerative diseases, Alzheimer's disease (AD) and Parkinson's disease (PD), remains inconclusive.

OBJECTIVE

This study aimed to evaluate the associations between long-term and short-term exposure to PM2.5 and PM10 (i.e., particulate matter with an aerodynamic diameter of, or smaller than, 2.5 μm or 10 μm), nitrogen dioxide (NO2), ozone, sulfur dioxide, and carbon monoxide and the risks of AD and PD.

METHODS

A random-effects model was used to summarize individual effect estimates in the meta-analysis. A subgroup meta-analysis was further conducted to explore the potential sources of heterogeneity.

RESULTS

In total, 42 eligible studies were included. For each 5 μg/m3 increase in long-term PM2.5 exposure, the odds ratios (ORs) were 1.16 (95% CI: 1.04, 1.30; I2 = 95%) and 1.10 (95% CI: 1.03, 1.17; I2 = 95%) for AD and PD, respectively. For each 5 μg/m3 increase in short-term PM2.5 exposure, the OR was 1.01 (95% CI: 1.002, 1.01; I2 = 77%) for PD. For each 1 ppb increase in long-term NO2 exposure, the OR was 1.01 (95% CI: 1.0002, 1.02; I2 = 79%) for PD.

CONCLUSION

Ambient air pollution, particularly PM2.5, may contribute to the increased risks of neurodegenerative diseases including AD and PD.

Ambient air pollution and Alzheimer's disease and other dementias: a global study between 1990 and 2019

BACKGROUND

Emerging research found air pollution may be associated with incident Alzheimer's disease (AD) and other dementias. However, few studies have examined these associations at the global scale. This study aimed to assess the dynamic associations between ambient air pollution and the burden of AD and other dementias worldwide.

METHODS

This study synthesised 149 countries/territories between 1990 and 2019. These data include age-standardised mortality rate (ASMR) and disability-adjusted life-years (DALYs) of AD and other dementias, ambient air pollution (fine particulate matter [PM2.5], NO2 and O3 concentration) and a series of covariates were from various source. Average annual percentage changes (AAPCs) were calculated to investigate the temporal variations. Linear mixed models were adopted to assess the associations with single- and multi-pollutant separately. The associations between air pollution changes and the AD and other dementias were also examined using linear regression models. Stratified analyses by Global North-South divide and human development index were performed to explore the potential inequity in air pollution impacts.

RESULTS

During 1990-2019, the global ASMR, DALYs and O3 increased by 0.11%, 0.09%, and 0.17% per year, respectively. In contrast, PM2.5 and NO2 decreased by 0.33% and 0.14% per year, respectively. Each 10 µg/m3 increase in PM2.5 was associated with a 0.118 (95% confidence interval [CI]: 0.060 - 0.175) higher ASMR and 0.966 (95%CI: 0.321 - 1.611) higher DALYs after adjusting for all the covariates. The ASMR increased by 0.112 and the DALYs increased by 1.068 for each 10 µg/m3 increase in O3. The NO2-dementia associations were relatively weak. Stronger O3-dementia associations were found in the Global South than those in the Global North.

CONCLUSIONS

The burden of dementia is expected to increase globally, given the continuously expansion of the ageing population. Air pollution was found to be significantly associated with a higher burden of AD and dementia. As a persistent challenge in urban cities, air pollution demands strict regulatory control.

Dietary interventions in mitigating the impact of environmental pollutants on Alzheimer's disease - A review

Numerous studies linking environmental pollutants to oxidative stress, inflammation, and neurotoxicity have assigned pollutants to several neurodegenerative disorders, including Alzheimer's disease (AD). Heavy metals, pesticides, air pollutants, and endocrine disruptor chemicals have been shown to play important roles in AD development, with some traditional functions in amyloid-β formation, tau kinase action, and neuronal degeneration. However, pharmacological management and supplementation have resulted in limited improvement. This raises the interesting possibility that activities usually considered preventive, including diet, exercise, or mental activity, might be more similar to treatment or therapy for AD. This review focuses on the effects of diet on the effects of environmental pollutants on AD. One of the primary issues addressed in this review is a group of specific diets, including the Mediterranean diet (MeDi), Dietary Approaches to Stop Hypertension (DASH), and Mediterranean-DASH intervention for Neurodegenerative Delay (MIND), which prevent exposure to these toxins. Such diets have been proven to decrease oxidative stress and inflammation, which are unfavorable for neuronal growth. Furthermore, they contribute to positive changes in the composition of the human gut microbiota and thus encourage interactions in the Gut-Brain Axis, reducing inflammation caused by pollutants. This review emphasizes a multi-professional approach with reference to nutritional activities that would lower the neurotoxic load in populations with a high level of exposure to pollutants. Future studies focusing on diet and environment association plans may help identify preventive measures aimed at enhancing current disease deceleration.

Metabolomic profiling identifies signatures and biomarkers linking air pollution to dementia risk: A prospective cohort study

Exposure to air pollution has been associated with increased dementia. However, it remains unknown what specific metabolic mechanisms play a role in this relationship. We included 192,300 dementia-free participants from the UK Biobank cohort study. Annual concentrations of air pollution were assessed based on the residential address. Elastic net regression was performed to identify air pollution-related metabolites, and metabolic score was constructed. Cox regression models and covariate balancing generalized propensity scores (CBGPS) regression models were conducted to explore the longitudinal associations between air pollution/metabolic signatures and dementia risk. The underlying mechanisms between air pollution and dementia driven by metabolic signature or specific metabolites were also investigated. A total of 2592 incident dementia cases were documented. We identified the metabolite profiles in response to air pollution exposure, including 87 metabolites for PM2.5, 65 metabolites for PM10, 76 metabolites for NO2, and 71 metabolites for NOx. The air pollution-related metabolic signatures were associated with increased risk of dementia, with hazard ratios (HR) of 1.17 (95 % CI: 1.12, 1.22), 1.06 (95 % CI: 1.02, 1.11), 1.16 (95 % CI: 1.10, 1.21), and 1.17 (95 % CI: 1.12, 1.22) for PM2.5, PM10, NO2 and NOx, respectively. The associations persisted using causal models. Metabolic signatures mediated the associations between air pollution exposure and dementia risk, with mediation proportions ranging from 6.57 % to 12.71 %. Additionally, we observed that a metabolite known as free cholesterol in medium VLDL (M-VLDL-FC) played a crucial mediating role. Our study provides novel insights into the metabolic mechanisms linking air pollution exposure to dementia risk.

The influence of frailty: How the associations between modifiable risk factors and dementia vary

BACKGROUND

The Lancet Commission has highlighted 12 modifiable risk factors for dementia. However, the effects of addressing these risk factors among the heterogeneous older adult population is not fully understood. We compared the association between risk factors and dementia by frailty, conceptualized as an explanation for the underlying health heterogeneity in old age.

METHODS

Data were from the UK Biobank, a cohort study with over 500,000 participants aged 37-73 between 2006 and 2010. Frailty was measured by five criteria: slowness, weakness, exhaustion, inactivity, and shrinking. Participants meeting 0, 1-2, and 3-5 criteria were considered non-frail, prefrail, and frail, respectively. We included 13 modifiable risk factors. We used logistic regression to determine the associations of risk factors with 10-year dementia among non-frail, pre-frail, and frail individuals, respectively. Additionally, we adopted a g-computation method to estimate the individual and combined population intervention effects (PIE) of the risk factors for dementia.

RESULTS

Of 381,419 participants, 58.4 %, 38.2 %, and 3.4 % were classified as non-frail, pre-frail, and frail, respectively. Except for smoking, depression, and excessive alcohol use, the other 10 risk factors had a stronger association with dementia among frailer individuals. We observed the highest PIEs among frail individuals when considering hypothetical interventions targeting low education, physical inactivity, central obesity, social isolation, hearing impairment, hypertension, diabetes, high nitrogen dioxide (NO2) exposure, high exposure of particulate matter with a diameter less than or equal to 2.5 micrometers (PM2.5), and traumatic brain injury individually. For the hypothetical interventions targeting all 13 risk factors together, we found a graded increase in the PIE across frailty status.

CONCLUSION

The associations between modifiable risk factors and dementia were stronger among the frail. We advocate for incorporating frailty assessments to pinpoint those most likely to benefit from targeted risk factor interventions.

Air pollution, APOE genotype and risk of dementia among individuals with cardiovascular diseases: A population-based longitudinal study

Individuals with cardiovascular disease (CVD) are particularly vulnerable to dementia, but it remains unclear whether air pollution exposure links with higher risk of dementia among those with CVD. The data were derived from the UK Biobank study (UKB). Dementia-free participants with CVD at baseline were included. Air pollution exposure was assessed through land use regression models, including particulate matter (PM2.5, PM2.5-10, and PM10), nitrogen dioxide (NO2), and nitrogen oxides (NOX). A Cox proportional hazards model was used to investigate the associations between air pollution exposure and incident dementia among individuals with CVD. Air pollution was associated with dementia among individuals with CVD, and the hazard ratios of dementia associated with each interquartile range (IQR) μg/m3 increase in air pollution were 1.07 (95% CI: 1.02, 1.12) for PM2.5, 1.10 (95% CI: 1.04, 1.15) for PM10, 1.08 (95% CI: 1.03, 1.14) for NO2 and 1.05 (95% CI: 1.00, 1.09) for NOx. Associations between air pollution and all-cause dementia were found to be significant among individuals with hypertension. Adverse effects of air pollution were also observed for Alzheimer's dementia (AD) and vascular dementia (VaD), with a higher effect for AD. Observed associations remained similar in subgroups of APOE ε4 carriers and noncarriers, although there was a higher risk difference across different air pollution concentration among these individuals carrying APOE ε4. Air pollution emerges as a critical risk factor for dementia among individuals with CVD, regardless of genetic susceptibility indicated by the APOE genotype. Notably, individuals with hypertension might be susceptible to the adverse effects of air pollution, leading to a higher incidence of dementia. Understanding these impacts on dementia among individuals with CVD may promote better targeted prevention and clinical management strategies.

Joint Exposure to Multiple Air Pollutants, Genetic Susceptibility, and Incident Dementia: A Prospective Analysis in the UK Biobank Cohort

Objectives: This study aimed to evaluate the joint effects of multiple air pollutants including PM2.5, PM10, NO2, and NOx with dementia and examined the modifying effects of genetic susceptibility. Methods: This study included 220,963 UK Biobank participants without dementia at baseline. Weighted air pollution score reflecting the joint exposure to multiple air pollutants were constructed by cross-validation analyses, and inverse-variance weighted meta-analyses were performed to create a pooled effect. The modifying effect of genetic susceptibility on air pollution score was assessed by genetic risk score and APOE ε4 genotype. Results: The HR (95% CI) of dementia for per interquartile range increase of air pollution score was 1.13 (1.07∼1.18). Compared with the lowest quartile (Q1) of air pollution score, the HR (95% CI) of Q4 was 1.26 (1.13∼1.40) (P trend = 2.17 × 10-5). Participants with high air pollution score and high genetic susceptibility had higher risk of dementia compared to those with low air pollution score and low genetic susceptibility. Conclusion: Our study provides evidence that joint exposure to multiple air pollutants substantially increases the risk of dementia, especially among individuals with high genetic susceptibility.

Relationships of Residential Distance to Major Traffic Roads with Dementia Incidence and Brain Structure Measures: Mediation Role of Air Pollution

Background: Uncertainty exists regarding the operating pathways between near-roadway exposure and dementia incidence. We intend to examine relationships between proximity to major roadways with dementia incidence and brain MRI structure measures, and potential mediation roles of air and noise pollution. Methods: The cohort study was based on the UK Biobank. Baseline survey was conducted from 2006 to 2010, with linkage to electronic health records conducted for follow-up. Residential distance to major roadways was ascertained residential address postcode. A land use regression model was applied for estimating traffic-related air pollution at residence. Dementia incidence was ascertained using national administrative databases. Brain MRI measures were derived as image-derived phenotypes, including total brain, white matter, gray matter, and peripheral cortical gray matter. Results: We included 460,901 participants [mean (SD) age: 57.1 (8.1) years; men: 45.7%]. Compared with individuals living >1,000 m from major traffic roads, living ≤1,000 m was associated with a 13% to 14% higher dementia risk, accounting for 10% of dementia cases. Observed association between residential distance and dementia was substantially mediated by traffic-related air pollution, mainly nitrogen dioxide (proportion mediated: 63.6%; 95% CI, 27.0 to 89.2%) and PM2.5 (60.9%, 26.8 to 87.0%). The shorter residential distance was associated with smaller volumes of brain structures, which was also mediated by traffic-related air pollutants. No significant mediation role was observed of noise pollution. Conclusions: The shorter residential distance to major roads was associated with elevated dementia incidence and smaller brain structure volumes, which was mainly mediated by traffic-related air pollution.

Associations of air pollution with all-cause dementia, Alzheimer's disease, and vascular dementia: a prospective cohort study based on 437,932 participants from the UK biobank

Objective

To prospectively assess whether air pollution, including PM2.5, PM10, and NOx, is associated with the risk of all-cause dementia, Alzheimer's disease (AD), and vascular dementia, and to investigate the potential relationship between air pollution and genetic susceptibility in the development of AD.

Methods and results

Our study included 437,932 participants from the UK Biobank with a median follow-up period of over 10 years. Using a Cox proportional hazards model, we found that participants exposed to PM2.5 levels of ≥10 μg/m3 had a higher risk of developing all-cause dementia (HR = 1.1; 95% CI: 1.05-1.28; p < 0.05) compared to the group exposed to PM2.5 levels of <10 μg/m3. However, there was no significant association between PM10 levels of ≥15 μg/m3 and the risk of all-cause dementia, AD, or vascular dementia when compared to the group exposed to PM10 levels of <15 μg/m3. On the other hand, participants exposed to NOx levels of ≥50 μg/m3 had a significantly higher risk of all-cause dementia (HR = 1.14; 95% CI: 1.02-1.26; p < 0.05) and AD (HR = 1.26; 95% CI: 1.08-1.48; p < 0.05) compared to the group exposed to NOx levels of <50 μg/m3. Furthermore, we examined the combined effect of air pollution (PM2.5, PM10, and NOx) and Alzheimer's disease genetic risk score (AD-GRS) on the development of AD using a Cox proportional hazards model. Among participants with a high AD-GRS, those exposed to NOx levels of ≥50 μg/m3 had a significantly higher risk of AD compared to those in the group exposed to NOx levels of <50 μg/m3 (HR = 1.36; 95% CI: 1.03-1.18; p < 0.05). Regardless of air pollutant levels (PM2.5, PM10, or NOx), participants with a high AD-GRS had a significantly increased risk of developing AD. Similar results were obtained when assessing multiple variables using inverse probability of treatment weighting (IPTW).

Conclusion

Our findings indicate that individuals living in areas with PM2.5 levels of ≥10 μg/m3 or NOx levels of ≥50 μg/m3 are at a higher risk of developing all-cause dementia. Moreover, individuals with a high AD-GRS demonstrated an increased risk of developing AD, particularly in the presence of NOx ≥ 50 μg/m3.

Association of air pollution, genetic risk, and lifestyle with incident adult-onset asthma: A prospective cohort study

BACKGROUND

Numerous studies have explored the association of air pollution with asthma but have yielded conflicting results. The exact role of air pollution in the incidence of adult-onset asthma and whether this effect is modified by genetic risk, lifestyle, or their interaction remain uncertain.

METHODS

We conducted a prospective cohort study on 298,738 participants (aged 37-73 years) registered in the UK Biobank. Cox proportional hazard models were used to evaluate the association of air pollution, including particulate matter (PM_2.5, PM_coarse, and PM₁₀), nitrogen dioxide (NO₂), and nitrogen oxides (NO_x), with asthma incidence. We constructed genetic risk and lifestyle scores, assessed whether the impact of air pollution on adult-onset asthma risk was modified by genetic susceptibility or lifestyle factors, and evaluated the identified interactions.

RESULTS

We found that each interquartile range increase in annual concentrations of PM_2.5, NO₂, and NO_x was related to 1.04 (95% confidence interval [CI]: 1.01, 1.08), 1.04 (95% CI: 1.00, 1.08), and 1.03 (95% CI: 1.00, 1.06) times the risk of adult-onset asthma, respectively. The size of the effect of air pollution was greater among subpopulations with low genetic risk or unfavorable lifestyles. We also identified an additive interaction effect of air pollution with lifestyle factors, but not with genetic risk, on the risk of adult-onset asthma.

CONCLUSION

Our analyses show that air pollution increases the risk of adult-onset asthma, but that the size of the effect is modified by lifestyle and genetic risk. These findings emphasize the need for integrated interventions for environmental pollution by the government as well as adherence to healthy lifestyles to prevent adult-onset asthma.

Association of Combined Exposure to Ambient Air Pollutants, Genetic Risk, and Incident Rheumatoid Arthritis: A Prospective Cohort Study in the UK Biobank

BACKGROUND

Evidence for a potential link between air pollution and rheumatoid arthritis (RA) is inconsistent, and the modified effect of genetic susceptibility on the relationship between air pollution and RA has not been well studied.

OBJECTIVE

Using a general population cohort from the UK Biobank, this study aimed to investigate the associations between various air pollutants and the risk of incident RA and to further estimate the impact of combined exposure to ambient air pollutants on the risk of developing RA under the modification effect of genetic predisposition.

METHODS

A total of 342,973 participants with completed genotyping data and who were free of RA at baseline were included in the study. An air pollution score was constructed by summing the concentrations of each pollutant weighted by the regression coefficients with RA from single-pollutant models to assess the combined effect of air pollutants, including particulate matter (PM) with diameters ≤ 2.5 μ m (PM 2.5 ), between 2.5 and 10 μ m (PM 2.5 - 10 ), and ≤ 10 μ m (PM 10 ), as well as nitrogen dioxide (NO 2 ) and nitrogen oxides (NO x ). In addition, the polygenic risk score (PRS) of RA was calculated to characterize individual genetic risk. The Cox proportional hazard model was used to estimate hazard ratios (HRs) and 95% confidence intervals (95% CIs) of associations of single air pollutant, air pollution score, or PRS with incident RA.

RESULTS

During a median follow-up time of 8.1 y, 2,034 incident events of RA were recorded. The HRs (95% CIs) of incident RA per interquartile range increment in PM 2.5 , PM 2.5 - 10 , PM 10 , NO 2 , and NO x were 1.07 (1.01, 1.13), 1.00 (0.96, 1.04), 1.01 (0.96, 1.07), 1.03 (0.98, 1.09), and 1.07 (1.02, 1.12), respectively. We also found a positive exposure-response relationship between air pollution score and RA risk (p Trend = 0.000053 ). The HR (95% CI) of incident RA was 1.14 (1.00, 1.29) in the highest quartile group compared with the lowest quartile group of the air pollution score. Furthermore, the results of the combined effect of air pollution score and PRS on the RA risk showed that the risk of RA incidence in the highest genetic risk and air pollution score group was almost twice that of the lowest genetic risk and air pollution score group [incidence rate (IR) per 100,000 person-years: 98.46 vs. 51.19, and HR = 1.73 (95% CI: 1.39, 2.17) vs. 1 (reference)], although no statistically significant interaction between the air pollution and genetic risk for incident RA was found (p Interaction > 0.05 ).

DISCUSSION

The results revealed that long-term combined exposure to ambient air pollutants might increase the risk of RA, particularly in those with high genetic risk. https://doi.org/10.1289/EHP10710.

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.