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.