Traffic noise and cardiovascular disease

Sammanfattning: Traffic noise is an increasing problem in urban areas worldwide, but health effects in relation to traffic noise exposure are not well understood. Several studies show that noise may give rise to acute stress reactions, possibly leading to cardiovascular effects, but the evidence is limited on cardiovascular risks associated with traffic noise exposure. Cardiovascular effects have been indicated for other environmental stressors such as occupational noise exposure and job strain. However, interactions between these factors in relation to cardiovascular disease have not been investigated. Furthermore, studies regarding interactions between air pollution and noise from road traffic in relation to cardiovascular disease are lacking. The overall aim of this thesis was to investigate the association between traffic noise exposure and cardiovascular disease, including interactions with other factors. The thesis is based on one case-control study and one cross-sectional study. The population based case-control study on risk factors in relation to first time myocardial infarction was conducted 1992-1994 in Stockholm County. The participants answered a questionnaire and underwent a physical examination. Exposure assessments were made of residential road traffic noise exposure, occupational noise exposure and air pollution between 1970 and 1992-94. Job strain was defined based on questionnaire data regarding the last employment. An increased risk of myocardial infarction was suggested in participants exposed to road traffic noise at the residence. The risk appeared particularly high among participants exposed to a combination of road traffic noise, occupational noise and job strain (OR 2.27, 95% CI 1.41 3.64). The association between road traffic noise and myocardial infarction did not seem to be affected by air pollution. The cross-sectional study was carried out in six European countries. All participants were interviewed at home and blood pressure measurements were made by a field nurse. An association was found between night-time aircraft noise exposure and hypertension. In a subgroup of study participants cortisol was assessed through saliva samples as an indicator of stress. We observed an elevation in morning saliva cortisol level among women exposed to high levels of aircraft noise at the residence of 34%, corresponding to 6.07 nmol/L (95% CI 2.32-9.81). No clear association was seen in men. It may be concluded that long-term traffic noise exposure at the residence seems to give rise to cardiovascular effects. Our results support the hypothesis that exposure to a combination of noise and job strain increases the risk of myocardial infarction substantially. In addition, our results suggest that exposure to aircraft noise increases the risk of hypertension, as well as morning saliva cortisol levels in women, which may be of relevance for noise-related cardiovascular effects.