Road traffic noise, air pollution and cardiovascular events in a Swedish cohort

Urbanization and increasing road traffic cause exposure to both noise and air pollution. While the levels of air pollutants such as nitrogen oxides (NO_x) have decreased in Sweden during the past decades, exposure to traffic noise has increased. The association with cardiovascular morbidity is less well established for noise than for air pollution, and most studies have only studied one of the two highly spatially correlated exposures. The Swedish Primary Prevention Study cohort consists of men aged 47 to 55 when first examined in 1970-1973. The cohort members were linked to the Swedish patient registry through their personal identity number and followed until first cardiovascular event 1970-2011. The address history during the entire study period was used to assign annual modelled residential exposure to road traffic noise and NO_x. The Cox proportional hazards model with age on the time axis and time-varying exposures were used in the analysis. The results for 6304 men showed a non-significant increased risk of cardiovascular disease for long-term road traffic noise at the home address, after adjusting for air pollution. The hazard ratios were 1.08 (95% CI 0.90-1.28) for cardiovascular mortality, 1.14 (95% CI 0.96-1.36) for ischemic heart disease incidence and 1.07 (95% CI 0.85-1.36) for stroke incidence, for noise above 60 dB, compared to below 50 dB. This study found some support for cardiovascular health effects of long-term exposure to road traffic noise above 60 dB, after having accounted for exposure to air pollution.