Long-term exposure to road traffic noise is associated with increased incidence of primary hypertension, according to a prospective analysis of UK Biobank data.
Traffic noise has emerged as an important environmental risk factor for CVD since 2010, with road traffic noise being mostly investigated for the associated health effects, Kazem Rahimi, PhD, FRCP, DM, MSc, FESC, professor of cardiovascular medicine and population health at the University of Oxford, U.K., and colleagues wrote in JACC: Advances. Research suggests that traffic noise can disturb sleep, activating the autonomic system and overproducing stress hormones, with subsequent activation of the renin-angiotensin-aldosterone system.
“Exposure to road traffic increases the risk of developing hypertension and this association is largely independent of air pollution, which also increases blood pressure,” Rahimi told Healio. “This should increase awareness of an important environmental risk factor for elevated blood pressure. Unfortunately, people cannot easily change their living environment. New policies are required to mitigate noise pollution.”
In a prospective, population-based analysis, Rahimi and colleagues analyzed data from more than 240,000 participants enrolled in the UK Biobank cohort study who were free of hypertension at baseline. The mean age of participants at recruitment was 55 years and 54.6% were women. Road traffic noise was estimated at baseline residential address using the common noise assessment method model.
“Detailed information on road traffic flow, vehicle classification, point source representation of a vehicle, and vehicle sound power emission was integrated in the road-traffic noise model, as well as parameters such as noise propagation, meteorological conditions, land over, building heights, and topography,” the researchers wrote. “Annual mean A-weighted sounds pressure level in decibels (dB[A]) for 2009 was assessed based on all road sources within 500 meters of residential address in the study.”
Researchers assessed two indicators of road traffic noise exposure: Lden, defined as the weighted average 24-hour road traffic noise level, with a 5-dB and 10-dB penalty added to the evening and night levels, respectively, and Lnight, defined as the average nighttime road traffic noise level. Researchers determined incident hypertension through March 2017 via linkage with medical records.
The mean residential Lden was 56 dB[A], with a range from 51.5 dB[A] to 87 dB[A]. Those exposed to Lden greater than 55 dB[A] and Lnight greater than 45 dB[A] accounted for 48% and 58.5% of study participants, respectively.
During a median of 8.1 years follow-up, researchers observed 21,140 incident primary hypertension diagnoses.
The HR for a 10 dB[A] increment in Lden exposure was 1.07 (95% CI, 1.02-1.13). A dose-response relationship was found (HR = 1.13; 95% CI, 1.03-1.25) for Lden greater than 65 dB[A] vs. 55 dB[A] or less (P for trend < .05).
The associations persisted after adjustment for fine particle pollution and nitrogen dioxide.
High exposure to road traffic noise and air pollution was associated with the highest hypertension risk, according to the researchers.
“It seems plausible that high levels of exposure to air pollution renders the body more sensitive to the hazardous effects of road traffic noise and vice versa,” the researchers wrote. “There are some potential mechanisms for the synergistic effects. Road traffic noise and air pollution are considered as triggers of hypertension, and they share some overlapping mechanisms, such as via vascular dysfunction, peripheral vasoconstriction, systemic inflammation and hypothalamus-pituitary adrenal axis activation, which may result in elevated blood pressure, and over the long-term lead to hypertension.”
Given that nearly 3 million people in the U.K. are exposed to road traffic noise greater than 65 dB, the researchers wrote, the 13% increased risk for incident primary hypertension seen with such noise levels in this study has potentially important implications for the disease burden from hypertension.
“Our results show that long-term residential exposure to road traffic noise is associated with elevated risk of incident primary hypertension,” they wrote. “Furthermore, the effects are exacerbated by higher air pollution levels. Given the ubiquitous presence of road traffic noise and air pollution, these findings highlight the importance of minimizing exposure to road traffic noise and air pollution levels.”
In a related editorial, Jiandong Zhang, MD, and Brian Kelley, MD, both cardiovascular disease fellows in the division of cardiology at University of North Carolina School of Medicine, wrote that studies suggest population-based approaches to reduce hypertension incidence show greater potential compared with individually targeted strategies.
“For example, a BP-lowering effect of as little as 2 mm Hg at the general populational level would result in a 17% reduction in the incidence of hypertension,” Zhang and Kelley wrote. “The data demonstrated in this article provide a higher quality of evidence to justify the potential to modify road traffic noise and air pollution from both individual and societal levels in improving cardiovascular health — namely, hypertension prevention.”
Additionally, pandemic-related lockdowns dramatically changed environmental factors, with fewer cars on the road, more flexible work schedules to reduce commuting and widely used face masks, they wrote.
“While we are embracing the reopening in the post-COVID era, some of those measures during the pandemic time might be worth a look when individuals and society prepare to tackle hypertension caused by road traffic-related noise and air pollution,” Zhang and Kelley wrote.