Long-term exposure to higher road traffic noise linked to increased risk of hypertension

3rd April 2023

Exposure to higher road traffic noise over time is linked to a higher incidence of hypertension particularly if there is higher air pollution

In a prospective study, Chinese and UK researchers have found that long-term exposure to high levels of road traffic noise (RTN), especially when levels of air pollution are also increased, is associated with an increased risk for the development of hypertension.

Hypertension is the leading cause of cardiovascular disease and premature death worldwide with one estimate suggesting that 349 million in high-income countries are affected by the condition. While modification of lifestyle factors such as a reduced intake of sodium, stopping smoking and increased physical activity are an integral part of the overall management strategy for the disease, it has become recognised that road traffic noise exposure is associated with increased risk of premature arteriosclerosis, coronary artery disease, and stroke. Moreover, the World Health Organisation (WHO) has suggested that there is high quality evidence linking road traffic road and ischaemic heart disease. However, while the WHO has found evidence linking noise from air, road, or rail traffic with hypertension, they considered the quality of the supportive evidence to be ‘very low’. Although some data indicates that exposure to RTN increases both systolic and diastolic blood pressure, it remains uncertain if exposure might actually cause hypertension.

In the current study, researchers examined information held in the UK Biobank to evaluate the association between long-term RTN exposure with incident primary hypertension. The RTN level was estimated with common noise assessment methods and the development of hypertension through linkage with medical records.

Road traffic noise and incident hypertension

A total of 246,447 individuals with mean age of 55 years (54.6%) were included in the analysis. Over a median follow-up period of 8.1 years, there were 21,140 cases of incident primary hypertension recorded.

In fully adjusted models for continuous exposure to RTN, there was 7% increase in newly diagnosed hypertension per 10 dB [A] increment in the mean weighted average 24-hour road traffic noise level (hazard ratio, HR = 1.07, 95% CI 1.02 – 1.13). Interestingly, exposure to the highest level of RTN (> 65 db[A]), and the highest levels of air pollution, based on both fine particles and nitrogen dioxide, posed the greatest risk for incident hypertension (HR = 1.22 for fine particles, HR = 1.18 for nitrogen dioxide).

The authors concluded that long-term exposure to road traffic noise was associated with an increased incidence of primary hypertension and that this effect was stronger in presence of higher air pollution.

Citation
Huang J et al. Road Traffic Noise and Incidence of Primary Hypertension: A Prospective Analysis in UK Biobank. JACC Adv 2023

Higher ozone levels linked to increased risk of hospital admission for cardiovascular diseases

30th March 2023

Increased ozone pollution has been associated with an increased risk of hospital admission for a range of cardiovascular diseases

Higher atmospheric ozone levels have been linked to a greater risk of a hospital admission for a range of adverse cardiovascular events according to the findings of a time-series analysis by Chinese researchers.

Although there are a number of clearly recognised risk factors for cardiovascular disease, recent studies generally support positive associations of exposure to chemical environmental stressors such as air pollution, with an increased risk for cardiovascular mortality and morbidity. Moreover, some evidence points to adverse effects associated with exposure to ozone and which appears to affect several pathways associated with cardiovascular disease. In addition, other work found a statistically significant association between short-term changes in ozone and mortality for 95 large US urban communities. However, while these data link ozone with mortality, much less is known about the association between the gas and cardiovascular morbidity and for which, hospital admissions, could serve as a useful proxy.

In the current study, Chinese researchers undertook a multi-city, time-series study to explore the associations of exposure to ambient ozone with daily hospital admissions for cardiovascular diseases over a two-year period. The city-specific daily concentrations of 8-hour maximum average ozone (O₃) and 24-hour average of O₃ were obtained, together with data on both fine particles (PM_2.5), inhaled particles (PM₁₀), and other gases such as sulphur and nitrogen dioxide and carbon monoxide.

Ozone pollution levels and risk of hospital admissions for cardiovascular disease

During the two-year period, there were 6,444,441 hospital admissions for adverse cardiovascular events in the 70 cities included in the study.

The results showed that a 10 μg/m³ increment in the two-day average daily, 8-hour maximum ozone concentrations, was associated with an increased risk for admission of 0.46% for coronary heart disease, 0.45% for angina pectoris, 0.75% for acute myocardial infarction and 0.41% for ischaemic stroke.

In fact, the researchers also calculated the excess risk attributable to higher ozone levels and different adverse cardiovascular events. For example, that there was a 6.52% excess risk of an acute myocardial infarction (AMI) for a high O₃ concentrations (≥100 μg/m³) compared to lower levels of < 70 μg/m³, which is considered to be naturally occurring level that is not due to human activity. Furthermore, the AMI risks were also elevated by 3.28% when ozone levels were ≥ 70 μg/m³ and 2.35% for levels between 70 and 99 μg/m³.

The authors concluded that ambient ozone was associated with increased risk of hospital admission for cardiovascular events and which was higher as levels of the gas increased. They added that these data should prompt the need for greater control of high ozone pollution.

Citation
Jiang Y et al. Ozone pollution and hospital admissions for cardiovascular events. Eur Heart J 2023