Does air pollution confound associations between environmental noise and cardiovascular outcomes? - A systematic review

Air pollution, greenspace, and metabolic syndrome in older Czech and Swiss populations

Background

The prevalence of metabolic syndrome (MetS) has increased rapidly, with considerable variation between European countries. The study examined the relationship between air pollutants, greenspace, and MetS and its components in the Czech and Swiss populations.

Methods

Cross-sectional data from the Czech Health, Alcohol and Psychosocial Factors in Eastern Europe (HAPIEE) (n = 4,931) and the Swiss cohort Study on Air Pollution and Lung and Heart Diseases in Adults (SAPALDIA) (n = 4,422) cohorts included participants aged 44-73 years. MetS was defined as abdominal obesity plus two additional components (hypertension, diabetes, low high-density lipoprotein cholesterol, and elevated triglycerides). Annual mean concentrations of PM10, PM2.5, NO2, and greenspace (defined as the annual mean of normalized difference vegetation index within 500 m) were assigned to the individual residential level. We estimated odds ratios (OR) using multivariable logistic regressions with cluster-robust standard error, controlling for multiple confounders.

Results

The prevalence of MetS was significantly higher in the Czech (51.1%) compared with Swiss (35.8%) population as were the concentration means of PM10 and PM2.5. In HAPIEE, a 5 μg/m3 increase in PM2.5 was associated with 14% higher odds of MetS (OR = 1.14; 95% confidence interval [CI] = 1.01, 1.28). In SAPALDIA, no evidence was found for the associations between air pollutants and MetS (e.g. OR = 1.01; 95% CI = 0.90, 1.13 for PM2.5). No protective effects of normalized difference vegetation index on MetS were observed. Upon inspection of MetS components, PM2.5 and PM10 exposures were associated with higher odds of hypertension and elevated triglycerides in HAPIEE only, while PM2.5, PM10, and NO2 were associated with higher odds of diabetes in SAPALDIA only.

Conclusion

Individuals with higher exposures to PM2.5 may be at higher risk of MetS. The differential associations with MetS components between the cohorts deserve further investigation.

Assessment of long-term exposure to traffic-related air pollution: An exposure framework

BACKGROUND

Exposure to ambient air pollution is associated with morbidity and mortality, making it an important public health concern. Emissions from motorized traffic are a common source of air pollution but evaluating the contribution of traffic-related air pollution (TRAP) emissions to health risks is challenging because it is difficult to disentangle the contribution of individual air pollution sources to exposure contrasts in an epidemiological study.

OBJECTIVE

This paper describes a new framework to identify whether air pollution differences reflect contrasts in TRAP exposures. Because no commonly measured pollutant is entirely specific to on-road motor vehicles, this exposure framework combined information on pollutants, spatial scale (i.e., geographic extent), and exposure assessment methods and their spatial scale to determine whether the estimated effect of air pollution in a given study was related to differences in TRAP.

METHODS

The exposure framework extended beyond the near-road environment to include differences in exposure to TRAP at neighborhood resolution ( ≤ 5 km) across urban, regional, and national scales. It also embedded a stricter set of criteria to identify studies that provided the strongest evidence that exposure contrasts were related to differences in traffic emissions.

RESULTS

Application of the framework to the transparent selection of epidemiological studies for a systematic review produced insights on assessing and improving comparability of TRAP exposure measures, particularly for indirect measures such as distances from roads. It also highlighted study design challenges related to the duration of measurements and the structure of epidemiological models.

IMPACT STATEMENT

This manuscript describes a new exposure framework to identify studies of traffic-related air pollution, a case study of its application in an HEI systematic review, and its implications for exposure science and air pollution epidemiology experts. It identifies challenges and provides recommendations for the field going forward. It is important to bring this information to the attention of researchers in air pollution exposure science and epidemiology because applying the broader lessons learned will improve the conduct and reporting of studies going forward.

Transportation noise and the cardiometabolic risk

Transportation noise is a widespread and often underestimated environmental pollutant, posing a substantial health risk particularly in urban areas. In contrast to air pollution, the health effects of noise pollution are less extensively documented. Defined as an unwanted and/or harmful sound, noise pollution affects over 20 % of the European Union (EU) population, contributing to an estimated 12,000 premature deaths and 48,000 new cases of ischemic heart disease annually. Recent epidemiological evidence strengthens the link between transportation noise and cardiovascular disease (CVD). A 2024 Umbrella + review with subsequent meta-analyses found that road traffic noise was associated with risk of CVD, more specifically a 4.1 % higher risk for ischemic heart disease, 4.6 % for stroke, and 4.4 % for heart failure per 10 dB(A). Translational and experimental studies have investigated the biological mechanisms behind noise-induced cardiovascular damage, showing that noise impacts stress and sleep pathways. Human studies reveal that nighttime noise impairs vascular function, elevates stress hormone levels, and triggers inflammation and oxidative stress, particularly in individuals with pre-existing CVD. Animal research corroborates these findings, demonstrating that noise exposure leads to endothelial dysfunction, elevated blood pressure, and oxidative stress through mechanisms shared with traditional cardiovascular risk factors. Mitigation strategies are crucial to reducing the health impacts of environmental noise. For road traffic, transitioning to electric vehicles offers minimal noise reduction, necessitating measures such as noise-reducing asphalt, low-noise tyres, and changes in urban infrastructure, whereas for aircraft noise nighttime flight bans and optimized flight paths are important tools for reducing noise exposure. Addressing co-exposure to noise and air pollution is essential for a comprehensive approach to mitigating the environmental burden on cardiovascular health.

Exploring the interaction between ambient air pollution and road traffic noise on stroke incidence in ten Nordic cohorts

INTRODUCTION

Ambient air pollution and road traffic noise are stroke risk factors, but evidence on their potential joint effects remains limited. This study investigated the independent and joint associations of air pollution and road traffic noise on stroke incidence using both multiplicative and additive scales.

METHODS

We followed stroke incidence in ten cohorts in Sweden, Denmark, and Finland. We modelled annual average levels of outdoor particulate matter < 2.5 µm (PM2.5), nitrogen dioxide (NO2) and road traffic noise at residential addresses. We applied Cox proportional hazards regression to evaluate their single association. We assessed multiplicative interaction with interaction terms in Cox models and additive interaction using the Relative Excess Risk due to Interaction method.

RESULTS

We followed 136,897 adults for 20 years, and 8.0 % experienced stroke incidence. PM2.5, NO2 and road traffic noise were associated with higher stroke risk in single-exposure models. Multiplicative models showed higher HRs between PM2.5 and stroke at higher levels of noise and vice versa: HRs per 5 μg/m3 of PM2.5 were 1.06 (95 % CI:0.94-1.21) at 40 dB and 1.11 (95 % CI:0.85-1.44) at 80 dB of road traffic noise; HRs per 12 dB of road traffic noise were 1.06 (95 % CI:1.01-1.11) at 4 μg/m3 and 1.17 (95 % CI:0.82-1.68) at 48 μg/m3 of PM2.5. Additive models showed that the combined association of PM2.5 and road traffic noise was 4 % (RERI = 0.04 (95 % CI:-0.05;1.12)) higher than the sum of their individual association.

CONCLUSION

PM2.5 and road traffic noise showed a non-significant synergistic association on stroke incidence.

Literature Review: Effects of Environmental Noise on the Cardiovascular Health

The adverse effects of environmental noise on human health have been recognized for more than a century. In particular, during the last decades, the vast majority of studies have focused on the detrimental role of noise in the induction of cardiovascular diseases. In this study, we aim to conduct a literature review on chronic stress responses induced by environmental noise, the risk of cardiovascular disease, and the underlying pathophysiological mechanisms. We retrieved the publications from the PubMed database by searching for "noise AND cardiovascular." By reviewing these publications in this study, we will first describe the epidemiologic research on cardiovascular risk factors and diseases induced by environmental noise, then discuss the mechanism(s) underlying these noise-induced cardiovascular impairments based on clinical and experimental studies, and finally evaluate the strategies to mitigate the effects of noise on cardiovascular health. We also evaluate the studies that describe the effects of noise level and noise intermittency, such as train noise, on cardiovascular health. We discuss whether environmental noise should be part of a risk factor profile for cardiovascular disease and how we should manage it, and assess the strategy that can be used to mitigate the noise-induced physiopathological changes. Furthermore, we briefly describe the effects of air pollution and heavy metals on cardiovascular health and discuss the relevance of these environmental stressors in the noise-induced cardiovascular disease. Our studies suggest that future studies are warranted to investigate new strategies that can mitigate the adverse effects of environmental noise on cardiovascular health.

Impact of air pollution and noise exposure on cardiovascular disease incidence and mortality: A systematic review

Background

The relationship between environmental pollutants, specifically air pollution and noise, and cardiovascular disease is well-recognized. However, their combined effects on cardiovascular health are not fully explored.

Objectives

To review evidence on the correlation between air pollution and noise exposure and cardiovascular disease incidence and mortality.

Methods

Following the PRISMA 2020 guidelines, we identified relevant studies through multiple databases and snowballing. We focused on studies published between 2003 and 2024. Studies were selected based on a PEOS framework, with a focus on exposure to air pollution or noise and clinical cardiovascular outcomes and evaluated for bias using the ROBINS-E tool.

Results

A total of 140 studies met our inclusion criteria. Most studies suggested a consistent association between long-term exposure to air pollutants and an increased risk of cardiovascular diseases, notably ischemic heart disease and stroke. While air pollution was often studied in isolation, the interaction effects between air pollution and noise exposure were less commonly investigated, showing mixed results. The majority of these studies were conducted in Western countries, which may limit the generalizability of the findings to global populations. No studies were found to use time-updated confounders, despite the long durations over which participants were followed, which could influence the accuracy of the results. Moreover, none of the studies incorporated both residential and occupational addresses in exposure assessments, suggesting a need for future studies to include these multiple exposure points to improve measurement precision and accuracy.

Conclusion

Air pollution exposure is increasingly linked to cardiovascular disease risks. Although individual air pollution and noise exposures are recognized as significant risk factors, the combined interaction between these exposures needs further exploration.

Registration

PROSPERO (CRD42023460443).

Road-traffic noise exposure and coronary atherosclerosis in the Swedish CArdioPulmonary bioImage Study (SCAPIS)

Background

Road-traffic noise may influence the development of cardiovascular events such as stroke and myocardial infarction, but etiological mechanisms remain unclear. This study aimed to assess the relationship between long-term road-traffic noise exposure and coronary atherosclerosis in Sweden.

Methods

In the Swedish CArdioPulmonary bioImage Study (SCAPIS) cohort, including 30,154 subjects aged 50-65 years, recruited between 2013 and 2018, coronary atherosclerosis was measured based on computer tomography (CT) scans as coronary artery calcium score, segment involvement score (SIS), and non-calcified plaques (NCP) at enrollment. Based on modified Nordic model, road-traffic noise exposure was modeled for 2000, 2013, and 2018 with interpolation for intermediate years. We investigated the association between time-weighted long-term exposure to road-traffic noise (Lden) and the prevalence of atherosclerosis using ordinal logistic regression models adjusting for potential socioeconomic, behavioral, and environmental confounders, including air pollution.

Results

No clear associations were found between road-traffic noise and coronary atherosclerosis. The odds ratio for coronary artery calcium score was 1.00 (95% confidence interval [CI] = 0.96, 1.04), SIS 0.99 (0.96, 1.03), and NCP 0.98 (0.90, 1.03) per interquartile range (9.4 dB Lden) for road-traffic noise exposure during 10 years before enrollment. No consistent associations were observed in site-specific analyses or using shorter exposure periods. Furthermore, exposure-response analyses revealed no clear trends, and there were no strong interactions between road-traffic noise and cardiovascular risk factors in relation to the atherosclerosis markers.

Conclusions

Long-term exposure to road-traffic noise was not linked to coronary atherosclerosis or calcification in relatively healthy, middle-aged populations in Sweden.

Long-term noise exposure and cause-specific mortality in chronic respiratory diseases, considering the modifying effect of air pollution

BACKGROUND

Chronic respiratory diseases (CRDs) are among the top three causes of human mortality. The relationship between modifiable environmental risk factor of noise and risk of mortality in CRDs is unclear. We investigated the longitudinal association between environmental noise exposure and cause-specific mortality in individuals with CRDs, considering the modifying effect of air pollution.

METHODS

Residential noise exposure was modelled using Common Noise Assessment Methods in Europe. Information on death causes were acquired from death registry data. Cox proportional-hazards models were used to estimate effect sizes.

RESULTS

Among 41,222 participants selected from UK Biobank with CRDs in baseline, a total of 3618 death cases occurred during an average follow-up of 12 years with mortality density of 7.16 per 1000 person years. Exposure with highest noise level (> percentile 90) were associated with 22 % (Hazard ratio [HR] = 1.22, 95 % confidence interval [CI]: 1.05, 1.42), 71 % (HR = 1.71, 95 % CI: 1.14, 2.56), and 84 % (HR = 1.84, 95 % CI: 1.10, 3.07) increased risks for all-cause, respiratory disease (RD)-cause, and COPD-cause mortalities, separately. Both multiplicative and additive interactions was found between air pollution and noise with the risk of RD-cause mortality. Participants with high air pollution and noise exposure were associated with a 101 % (HR = 2.01, 95 % CI: 1.10, 3.66) increased risk of RD-cause mortality.

CONCLUSION

It is imperative to mitigate noise exposure as a preventive measure against incident mortality in individuals with CRDs.

Long-term exposure to air pollution, road traffic noise and greenness, and incidence of myocardial infarction in women

BACKGROUND

Emerging evidence shows that long-term exposure to air pollution, road traffic noise, and greenness can each be associated with cardiovascular disease, but only few studies combined these exposures. In this study, we assessed associations of multiple environmental exposures and incidence of myocardial infarction using annual time-varying predictors.

MATERIALS AND METHODS

In a population-based cohort of 20,407 women in Sweden, we estimated a five-year moving average of residential exposure to air pollution (PM2.5, PM10 and NO2), road traffic noise (Lden), and greenness (normalized difference vegetation index, NDVI in 500 m buffers), from 1998 to 2017 based on annually varying exposures and address history. We used adjusted time-varying Cox proportional hazards regressions to estimate hazard ratios (HR) and 95 % confidence intervals (95 % CI) of myocardial infarction per interquartile range (IQR). Furthermore, we investigated interactions between the exposures and explored potential vulnerable subgroups.

RESULTS

In multi-exposure models, long-term exposure to greenness was inversely associated with incidence of myocardial infarction (HR 0.89; 95 % CI 0.80, 0.99 per IQR NDVI increase). Stronger associations were observed in some subgroups, e.g. among women with low attained education and in overweight (BMI ≥ 25 kg/m2) compared to their counterparts. For air pollution, we observed a tendency of an increased risk of myocardial infarction in relation to PM2.5 (HR 1.07; 95 % CI 0.93, 1.23) and the association appeared stronger in women with low attained education (HR 1.30; 95 % CI 1.06, 1.58). No associations were observed for PM10, NO2 or road traffic noise. Furthermore, there were no clear interaction patterns between the exposures.

CONCLUSION

Over a 20-year follow-up period, in multi-exposure models, we found an inverse association between residential greenness and risk of myocardial infarction among women. Furthermore, we observed an increased risk of myocardial infarction in relation to PM2.5 among women with low attained education. Road traffic noise was not associated with myocardial infarction.

Statistical Analysis Plan for the AIRCARD Study: Individual Long-Term Air and Noise Pollution Exposure and Cardiovascular Disease Incidence and Mortality - A Prospective Cohort Study Utilizing DANCAVAS and VIVA Screening Trials

INTRODUCTION

The AIRCARD study is designed to investigate the relationship between long-term exposure to air and noise pollution and cardiovascular disease incidence and mortality. We aim to conduct a robust prospective cohort analysis assessing the cumulative and differential impacts of air and noise pollution exposure on cardiovascular disease and mortality. This study will adjust for relevant confounders, including traditional cardiovascular risk factors, socioeconomic indicators, and lipid-lowering agents.

METHODS

This prospective cohort study will include 27,022 male participants aged 65-74, recruited from the two large Danish DANCAVAS and VIVA trials, both population-based randomized, multicentered, clinically controlled studies. We will assess long-term exposure to air pollutants using the state-of-the-art DEHM/UBM/AirGIS modeling system and noise pollution through the Nord2000 and SoundPLAN models, covering data from 1979 to 2019. This statistical analysis plan is strictly formulated to predefine the analytical approach for all outcomes and key study variables before data access. The primary analysis will utilize Cox proportional hazards models, adjusted for confounders identified in our cohort (age, body mass index, hypertension, diabetes, smoking status, family history of heart disease, socioeconomic factors, and lipid-lowering agents). This statistical analysis plan further includes Spearman rank correlation to explore inter-pollutant associations.

CONCLUSION

The AIRCARD study addresses global concerns about the impact of air and noise pollution on cardiovascular disease. This research is important for understanding how the pollutants contribute to cardiovascular disease. We aim to provide insights into this area, emphasizing the need for public health measures to mitigate pollution exposure. Our goal is to provide policymakers and healthcare professionals with information on the role of environmental factors in cardiovascular health that could influence global strategies to reduce the cardiovascular disease burden associated with pollution. The design of this SAP ensures transparency and verifiability, considering the complexities of evaluating environmental health impacts over an extended period.

Long-term exposure to transportation noise and diabetes mellitus mortality: a national cohort study and updated meta-analysis

BACKGROUND

Long-term exposure to transportation noise is related to cardio-metabolic diseases, with more recent evidence also showing associations with diabetes mellitus (DM) incidence. This study aimed to evaluate the association between transportation noise and DM mortality within the Swiss National Cohort.

METHODS

During 15 years of follow-up (2001-2015; 4.14 million adults), over 72,000 DM deaths were accrued. Source-specific noise was calculated at residential locations, considering moving history. Multi-exposure, time-varying Cox regression was used to derive hazard ratios (HR, and 95%-confidence intervals). Models included road traffic, railway and aircraft noise, air pollution, and individual and area-level covariates including socio-economic position. Analyses included exposure-response modelling, effect modification, and a subset analysis around airports. The main findings were integrated into meta-analyses with published studies on mortality and incidence (separately and combined).

RESULTS

HRs were 1.06 (1.05, 1.07), 1.02 (1.01, 1.03) and 1.01 (0.99, 1.02) per 10 dB day evening-night level (Lden) road traffic, railway and aircraft noise, respectively (adjusted model, including NO2). Splines suggested a threshold for road traffic noise (~ 46 dB Lden, well below the 53 dB Lden WHO guideline level), but not railway noise. Substituting for PM2.5, or including deaths with type 1 DM hardly changed the associations. HRs were higher for males compared to females, and in younger compared to older adults. Focusing only on type 1 DM showed an independent association with road traffic noise. Meta-analysis was only possible for road traffic noise in relation to mortality (1.08 [0.99, 1.18] per 10 dB, n = 4), with the point estimate broadly similar to that for incidence (1.07 [1.05, 1.09] per 10 dB, n = 10). Combining incidence and mortality studies indicated positive associations for each source, strongest for road traffic noise (1.07 [1.05, 1.08], 1.02 [1.01, 1.03], and 1.02 [1.00, 1.03] per 10 dB road traffic [n = 14], railway [n = 5] and aircraft noise [n = 5], respectively).

CONCLUSIONS

This study provides new evidence that transportation noise is associated with diabetes mortality. With the growing evidence and large disease burden, DM should be viewed as an important outcome in the noise and health discussion.

Transportation Noise Pollution and Cardiovascular Health

Epidemiological studies have found that transportation noise increases the risk for cardiovascular morbidity and mortality, with solid evidence for ischemic heart disease, heart failure, and stroke. According to the World Health Organization, at least 1.6 million healthy life years are lost annually from traffic-related noise in Western Europe. Traffic noise at night causes fragmentation and shortening of sleep, elevation of stress hormone levels, and increased oxidative stress in the vasculature and the brain. These factors can promote vascular (endothelial) dysfunction, inflammation, and arterial hypertension, thus elevating cardiovascular risk. The present review focusses on the indirect, nonauditory cardiovascular health effects of noise. We provide an updated overview of epidemiological research on the effects of transportation noise on cardiovascular risk factors and disease, and mechanistic insights based on the latest clinical and experimental studies and propose new risk markers to address noise-induced cardiovascular effects in the general population. We will discuss the potential effects of noise on vascular dysfunction, oxidative stress, and inflammation in humans and animals. We will elaborately explain the underlying pathomechanisms by alterations of gene networks, epigenetic pathways, circadian rhythm, signal transduction along the neuronal-cardiovascular axis, and metabolism. We will describe current and future noise mitigation strategies. Finally, we will conduct an overall evaluation of the status of the current evidence of noise as a significant cardiovascular risk factor.

Health position paper and redox perspectives - Disease burden by transportation noise

Transportation noise is a ubiquitous urban exposure. In 2018, the World Health Organization concluded that chronic exposure to road traffic noise is a risk factor for ischemic heart disease. In contrast, they concluded that the quality of evidence for a link to other diseases was very low to moderate. Since then, several studies on the impact of noise on various diseases have been published. Also, studies investigating the mechanistic pathways underlying noise-induced health effects are emerging. We review the current evidence regarding effects of noise on health and the related disease-mechanisms. Several high-quality cohort studies consistently found road traffic noise to be associated with a higher risk of ischemic heart disease, heart failure, diabetes, and all-cause mortality. Furthermore, recent studies have indicated that road traffic and railway noise may increase the risk of diseases not commonly investigated in an environmental noise context, including breast cancer, dementia, and tinnitus. The harmful effects of noise are related to activation of a physiological stress response and nighttime sleep disturbance. Oxidative stress and inflammation downstream of stress hormone signaling and dysregulated circadian rhythms are identified as major disease-relevant pathomechanistic drivers. We discuss the role of reactive oxygen species and present results from antioxidant interventions. Lastly, we provide an overview of oxidative stress markers and adverse redox processes reported for noise-exposed animals and humans. This position paper summarizes all available epidemiological, clinical, and preclinical evidence of transportation noise as an important environmental risk factor for public health and discusses its implications on the population level.

Aircraft noise exposure and risk for recurrent cardiovascular events after acute coronary syndrome: A prospective patient cohort study

In several population based cohort studies associations between aircraft noise and various diagnoses of cardiovascular disease were observed. However, no study has yet addressed the risk of recurrences in relation to transportation noise in patients with acute coronary heart disease. We conducted a prospective patient cohort study of 737 individuals recruited from eleven cardiac centers in the Rhine-Main region in the vicinity of Frankfurt Airport. All patients had an angiographically confirmed acute coronary syndrome diagnosed between July 2013 and November 2018. Individual aircraft noise exposure at the place of residence was calculated using Soundplan software, and exposure to road traffic and railway noise was obtained from noise maps provided by the Hessian State Agency. Data was analyzed by means of Cox regression adjusted for relevant confounders. Recurrent event as non-fatal endpoint was defined as myocardial infarction, stroke, bypass surgery or percutaneous coronary intervention with stent implantation. In addition, all-cause mortality was evaluated. Follow-up data including socioeconomic and confounder information was obtained from 663 (90%) patients covering a mean follow-up period of 42 (range: 1-80) months. Mean Lden aircraft noise exposure was 48.1 dB. Adjusted hazard ratio (HR) for recurrence was 1.24 (95%-CI: 0.97-1.58) per 10 dB increase in Lden aircraft noise exposure. A combined analysis of recurrence and all-cause mortality yielded a HR of 1.31 (95%-CI: 1.03-1.66). Similar HRs were found for Lday and Lnight aircraft noise exposure. HRs for road traffic and railway noise were above unity but less pronounced and not significant. Observed exposure-response associations for aircraft noise were more pronounced than previously observed in population-based cohort studies suggesting that acute coronary heart disease patients are particularly vulnerable to effects from transportation noise. Measures to reduce environmental noise exposure may thus be helpful in improving clinical outcome of patients with coronary heart disease.