Abstract

BACKGROUND: Long-term exposure to aircraft noise has been associated with small increases in cardiovascular disease risk, but there are almost no short-term exposure studies. OBJECTIVES: Research questions were: Is there an association between short-term changes in exposure to aircraft noise and cardiovascular morbidity and mortality? What are the key effect modifiers? Is there variability in risk estimates between areas with consistent versus changing patterns of noise exposure? Do risk estimates differ when using different noise metrics? DESIGN: Descriptive analyses of noise levels and variability at different times of day, analyses of inequalities in noise exposure and case-crossover analyses of cardiovascular events in relation to aircraft noise exposure. SETTING: Area surrounding London Heathrow airport. TIME PERIOD: 2014-18. PARTICIPANTS: Whole population in study area. MAIN OUTCOME MEASURES: Cardiovascular disease hospitalisations and mortality. DATA SOURCES: Aircraft noise levels modelled using a standard noise model for: (1) daily equivalent continuous sound levels at different times of day; (2) daily number of events above defined noise thresholds (2018 only). National Health Service digital hospital admission records and Office for National Statistics mortality records for 2014-18 for cardiovascular outcomes, plus individual-level confounders available from healthcare records. Confounder data including road traffic noise (Leicester modelled), rail noise and air pollution (Department for Environment, Food and Rural Affairs), area level deprivation and ethnicity (UK Census). RESULTS: The morning shoulder period (06.00-07.00 hours) was the noisiest of all eight bands (mean: 50.92 dB). The morning shoulder period also had the third highest number of noisy events (flights) > 60 dB per day, with three events across postcodes on average. However, the highest number of noisy events occurred in daytime (highest between 07.00 and 15.00 hours, second highest 15.00 and 19.00 hours). To identify areas with high variability in aircraft noise exposure (due to changes in flight paths because of wind direction and airport operations), we used coefficients of variation (CoV). The period 24.00-04.30 hours had the highest mean CoV (67.33-74.16), followed by 04.30-06.00 hours and 23.00-24.00 hours. Postcodes in the least deprived quintiles of Carstairs index or avoidable death rate had the lowest noise levels. In case-crossover analyses, we observed increased risk for cardiovascular disease hospital admissions for evening noise 19.00-23.00 hours (odds ratio 1.005, 95% confidence interval 1.000 to 1.010 per 5 dB), but not for other periods or mortality. Further analyses suggested that increased risks were occurring in postcodes with low CoV for noise. We found effect modification by age, sex, ethnicity, deprivation and season. LIMITATIONS: The industry standard noise model, the Aviation Environmental Design Tool, used does not take account of wind direction, which may have led to some exposure misclassification. CONCLUSIONS: We developed a comprehensive dataset of daily aircraft noise variability. We found small associations between cardiovascular hospitalisations (but not deaths) and evening aircraft noise levels, particularly in areas with low variability of noise. FUTURE WORK: More studies are needed to understand the effect of noise variation and respite/relief on cardiovascular disease. FUNDING: This award was funded by the National Institute for Health and Care Research (NIHR) Public Health Research programme (NIHR award ref: 15/192/13) and is published in full in Public Health Research; Vol. 12, No. 13. See the NIHR Funding and Awards website for further award information.