Long-term exposure to transportation noise in relation to metabolic and cardiovascular outcomes

Abstract

Transportation noise exposure is increasing because of rapid urbanization and transportation growth. Environmental noise exposure affects a large part of the population and gives rise to widespread annoyance and sleep disturbances. However, the evidence on metabolic and cardiovascular effects of long-term exposure to transportation noise from different sources is mostly limited and of low quality, hampering comprehensive risk assessment, although such effects may be of great public health significance. The main aim of this thesis was to study the development of obesity and cardiovascular outcomes in relation to exposure to noise from road traffic, railways and aircraft, and particularly the role of interactions.

The four cohorts under study were based in Stockholm County and included a total of more than 22,000 adults followed for up to 20 years. Three of the papers in the thesis used only one of these cohorts, the SDPP cohort, including close to 8,000 subjects at recruitment. Individual assessment of exposure to noise from road traffic, railways or aircraft was based on a detailed residential history for each study participant as well as a newly developed database containing longitudinal information on determinants of noise levels generated by the three transportation noise sources. Data on air pollution exposure was obtained from dispersion models based on a similar methodology. Information on covariates and health outcomes was based on questionnaires and registers, and the health outcome data were further supplemented with information from clinical investigations.

For obesity markers, the strongest associations were observed in relation to aircraft noise. A 10 dB higher level in exposure was associated with a waist circumference increase and weight gain of 0.16 cm/year (95% CI 0.14–0.17) and 0.03 kg/year (95% CI 0.01–0.04), respectively. Road traffic noise exposure was related to a waist circumference increase of 0.04 cm/year (95% CI 0.02–0.06) per 10 dB Lden, while no clear association was observed for railway noise. The incidence rate ratio of central obesity in relation to number of sources of transportation noise exposure increased from 1.22 (95% CI 1.08–1.39) among those exposed to only one source to 2.26 (95% CI 1.55–3.29) among those exposed to all three transportation noise sources. Moreover, aircraft noise exposure was related to incidence of hypertension (hazard ratio: 1.16; 95% CI 1.08–1.24 per 10 dB Lden), but no associations appeared for other transportation noise sources. No clear or consistent associations were observed between transportation noise exposure and risk of ischemic heart disease (IHD) or stroke. However, there appeared to be an increased risk of IHD in women related to road traffic noise exposure, while the opposite held true for men. Higher risks appeared of both IHD and stroke incidence in those exposed to all three noise sources, with hazard ratios of 1.57 (95% CI 1.06–2.32) and 1.42 (95% CI 0.87–2.32), respectively.

In conclusion, our findings indicate adverse effects of long-term transportation noise exposure on some metabolic and cardiovascular outcomes, and suggest that combined exposure to different transportation noise sources may be particularly harmful.