Traffic noise and hypertension - results from a large case-control study.

BACKGROUND: Environmental traffic noise is a potential cause of hypertension. We aimed to study the association between hypertension as recorded in health insurance claims data and the exposure to three sources of traffic noise (aircraft, road and rail). METHODS: This large case-control study was conducted among persons aged 40 and above in 2010 and living in the region around Frankfurt airport in Germany. Individual residential noise exposure for the index year 2005 was assessed using standard noise algorithms. Cases were all newly diagnosed cases of hypertension recorded in three large health insurances databases in the period 2006-2010. Controls had no hypertension diagnosis. Categorical and continuous analyses were conducted with binary logistic regression models adjusted for sex, age and residential area-based socioeconomic information. RESULTS: The main analysis included 137,577 cases and 355,591 controls. There were no associations with any of the traffic noise sources. Odds ratios (OR) per 10dB noise increase were 0.99 (95% confidence interval: 0.98;1.01) for aircraft noise, and 1.00 (0.99;1.01) both for road and railway noise. Similarly, nighttime noise levels showed no associations with hypertension. Odds ratios were increased for the subgroup of newly diagnosed hypertension cases with a subsequent diagnosis of hypertensive heart disease: per 10dB aircraft noise there was a 13.9% OR increase (6.0% for road traffic, 5.4% for rail traffic). Increases were also noted when we analyzed cases with a longer exposure-outcome time window. CONCLUSION: Our results are suggestive of an association of noise exposure with clinically more severe hypertension diagnoses, but not with uncomplicated hypertension. The absence of individual confounder data, however, adds to the risk of bias. The results contribute to evidence on traffic noise as a cardiovascular risk factor.