Circadian chaos: How transportation noise harms heart health

By Tarun Sai LomteReviewed by Susha Cheriyedath, M.Sc.Dec 12 2024

Long-term exposure to transportation noise is silently harming heart health, disrupting sleep patterns, and amplifying cardiovascular risks—it's time to act on this hidden environmental threat.

Perspective: Noise causes cardiovascular disease: it’s time to act. Image Credit: Lisa-S / Shutterstock

In a recent study published in the Journal of Exposure Science and Environmental Epidemiology, researchers reviewed the metabolic and cardiovascular health effects of transportation noise.

The adverse health effects of environmental exposures on cardiovascular disease (CVD) have been well established. Recent studies have shown particular matter with ≤ 2.5 μm diameter as a major air pollutant, contributing to significant mortality. Moreover, proximity to major roads increases cardiovascular conditions, such as hypertension and ischemic heart disease (IHD).

However, whether these effects were from noise or air pollution remains unclarified. Noise is defined as harmful or unwanted sound and comes from industrial, transportation, leisure, occupational, and residential sources. Recent research underscores that noise pollution often overlaps with air pollution, compounding cardiovascular risks. Transportation noise has received much less attention despite suburban and urban areas experiencing high noise and air pollution levels. In the present study, researchers reviewed the metabolic and cardiovascular effects of transportation noise.

Exposure to Traffic Noise and Disease Burden

The European Environment Agency reported that many people were exposed to high road traffic noise levels in 2020. It estimated that one-fifth of the European Union (EU) population lived in areas with transportation noise above 55 dB. According to the World Health Organization (WHO), adverse health effects are likely to occur at these noise levels, especially at night when it should not exceed 45 dB.

Environmental noise in the EU is estimated to cause 48,000 IHD cases, 12,000 premature deaths, 22 million people enduring significant annoyance, and 6.5 million individuals experiencing chronic sleep disturbance annually. In the United States (US), 5.2 million, 7.9 million, and 7.8 million people were highly annoyed by road, rail, and aircraft traffic in 2020, respectively. Studies indicate that nighttime noise poses greater risks to cardiovascular health than daytime noise, due to its disruption of circadian rhythms and sleep quality.

Noise, Disease, and Mortality

Various studies have reported positive associations between road traffic noise and incident stroke. A recent meta-analysis indicated that road traffic noise was associated with a 5% increased heart failure risk. A Swiss study reported associations between short-term exposure to aircraft noise and CVD mortality, especially nighttime noise between 40 dB and 50 dB.

Cohort studies have linked transportation noise to a higher risk of diabetes. Further, noise may impact sleep quality and contribute to metabolic changes leading to diabetes. Moreover, research highlights noise's association with increased measures of adiposity, linking it to lifelong weight gain and obesity risks. Various reports indicate that road traffic noise is also associated with elevated measures of adiposity, suggesting that noise could impact body weight throughout life.

Effects of Noise on Vascular Function and the Immune System

Exposure to transportation noise has been reported to impact the immune system. Studies showed that noise elevates high-sensitivity C-reactive protein and interleukin-12 levels and reduces natural killer cell activity and population. Immune system alterations have been linked to increased noise sensitivity and circulating cortisol levels. Additionally, DNA methylation changes associated with chronic noise exposure suggest potential long-term impacts on inflammation and immune responses.

A Swiss cohort study observed that long-term exposure to air pollution and transportation noise resulted in distinct DNA methylation patterns and enriched pathways associated with immune response, inflammation, and cellular development. Moreover, chronic exposure to nocturnal intermittent road or rail traffic noise increased arterial stiffness in the same cohort.

Mechanistic Insights

Translational studies in individuals with and without CVD have shown that exposure to transportation noise for one night significantly increases oxidative stress markers in serum, with significant endothelial dysfunction. Preclinical studies demonstrated that the activation of NADPH oxidase and a dysfunctional endothelial nitric oxide synthase mainly drove oxidative stress in mice exposed to noise.

Previously, the study’s authors showed that noise exposure could dysregulate vasculature gene networks, further impairing vascular and endothelial signaling and contributing to cardiovascular dysfunction. Nighttime noise exposure had more detrimental effects than daytime exposure, likely due to circadian rhythm disruption and elevated stress hormone levels. The authors also reported dysregulation of the circadian clock, mainly through the downregulation of FOXO3.

Noise exposure also impacts the neuroendocrine system, increasing endothelin-1 and angiotensin-II levels; this increase elevates inflammation and oxidative stress within the microvasculature and conductance vessels of the brain, contributing to hypertension and other cardiovascular conditions. Furthermore, neural activity changes in the amygdala have been linked to arterial inflammation and heightened cardiovascular risk. The activation of the sympathetic nervous system due to oxidative stress leads to the release of catecholamines, which could aggravate cardiovascular damage.

Concluding Remarks

Transportation noise significantly impacts cardiovascular health through various mechanisms involving inflammation, oxidative stress, gene dysregulation, endothelial dysfunction, metabolic changes, and circadian rhythm disruption. Additionally, its interaction with air pollution exacerbates these risks, underlining the need for a multifaceted approach to mitigation. Taken together, noise should be acknowledged as a cardiovascular risk factor in the CVD prevention guidelines.

Further studies are required to assess interactions between noise and other environmental stressors and explore protective interventions.