The effect of aircraft, road, and railway traffic noise on stroke - results of a case-control study based on secondary data.

AIM: To examine the stroke risks associated with aircraft, road traffic, and railway noise exposure in a large case-control study. MATERIALS AND METHODS: All people aged ≥40 years living around the Frankfurt airport that were insured by one of three large statutory health insurance funds between 2005 and 2010 were included in the study (n = 1,026,670). Address-specific exposure to aircraft, road, and railway traffic noise was estimated for 2005. We used insurance claim data to identify 25,495 newly diagnosed cases of stroke between 2006 and 2010 and compared them with 827,601 control participants. Logistic regression analysis was used to calculate the odds ratios adjusted for age, sex, local proportion of people receiving unemployment benefits, and if available individual indicators of socioeconomic status (education, occupation). RESULTS: For 24-h continuous aircraft noise exposure, neither increased risk estimates nor a positive linear exposure-risk relation was found. However, stroke risk was statistically significantly increased by 7% [95% confidence intervals (95%CI): 2-13%] for people who were exposed to <40 dB of 24-h continuous aircraft noise, but ≥6 events of maximum nightly sound pressure levels ≥50 dB. For road and railway traffic noise, there was a positive linear exposure-risk relation: Per 10 dB the stroke risk increased by 1.7% (95%CI: 0.3-3.2%) for road traffic noise and by 1.8% (95%CI: 0.1-3.3%) for railway traffic noise. The maximum risk increase of 7% (95%CI: 0-14%) for road traffic noise and 18% (95%CI: 2-38%) for railway traffic noise was found in the exposure category ≥65 to <70 dB. CONCLUSION: This large case-control study indicates that traffic noise exposure may lead to an increase in stroke risk. It furthermore suggests that maximum aircraft noise levels at night increase the stroke risk even when continuous noise exposure is low, and thus highlights the relevance of maximum noise levels for research and policies on noise protection.

Aircraft Noise and the Risk of Stroke.

BACKGROUND: There have been many individual studies on the question whether air- craft noise is a risk factor for stroke, but until now there has not been any summary of the current state of the evidence of adequately high methodological quality. METHODS: In a systematic review and meta-analysis (PROSPERO registry number CRD42013006004), we evaluated the relation between address-based aircraft noise exposure and the incidence of stroke. A systematic literature search was performed in the MEDLINE, EMBASE, and BIOSIS databases including publications up to August 2017. Two of the authors, working independently of each other, screened the titles, abstracts, and full texts for eligible articles and evaluated the quality of the included studies on a three-level scale. The change of risk per 10 dB increase in the weighted mean aircraft noise level (LDEN) was calculated. LDEN is a noise level indicator with additional weighting of evening and nighttime noise. RESULTS: Of the nine studies that met the inclusion criteria, seven were suitable for inclusion in the meta-analysis. The result of the meta-analysis indicated a relative stroke risk of 1.013 (95% confidence interval, [0.998; 1.028]) per 10 dB increase in LDEN, corresponding with an estimated 1.3% increase in the risk of stroke for each additional 10 dB of aircraft noise. The underlying studies were of poor to medium quality. The analyses of the studies included adjustments for various combinations of confounders, including age, sex, ethnicity, and socioeconomic status. CONCLUSION: The present meta-analysis indicates that aircraft noise increases the risk of stroke, even if the overall finding just fails to reach statistical significance. The differing measures of exposure in the included studies, the lack of differentiation be- tween ischemic and hemorrhagic stroke, and the lack of consideration of maximum noise levels are all factors that may have led to a marked underestimation of the risk of stroke.