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.
Keywords: AIRCRAFT NOISE; CARDIOVASCULAR DISEASE; CORONARY HEART DISEASE; ENVIRONMENTAL NOISE; EPIDEMIOLOGY; STROKE.
Previous studies have found links between long-term aircraft noise exposure and heart disease or stroke, but there are very few such studies on short-term noise exposure. We first looked at how aircraft noise varies across the day in areas affected by noise from aircraft arriving at and departing from London Heathrow airport. We used standard noise models that use information such as flight paths, type of aircraft and weather conditions to estimate aircraft noise levels at different times of day near Heathrow airport in 2014–18. We found that the daytime periods 7 a.m.–7 p.m., with the largest number of flights, had higher noise levels than evening or night-time and higher numbers of noisy flights. However, the early morning (6 a.m.–7 a.m. had the highest average noise levels. Night-time aircraft noise levels were lower but fluctuated more than at any other time of day. We investigated inequalities in noise exposures by comparing wealthy with less wealthy areas and found that wealthier areas tended to have lower aircraft noise levels, especially at night. We then examined whether higher noise levels at particular times of day in an area were linked with higher hospital admissions and deaths from heart disease or stroke (cardiovascular disease). We saw a small increased risk of hospital admissions for cardiovascular disease if there were high evening noise levels the previous day. This may be linked to sleep disturbance. Men aged over 65 years also showed increased risks associated with daytime aircraft noise. Finally, we assessed whether areas prone to changing aircraft noise patterns (i.e. with relief periods from aircraft noise) affected the increased risk of cardiovascular disease in areas with higher noise in the evenings and found the higher risks were only seen in areas with more constant noise levels. More research is needed to investigate potential health benefits of relief periods with lower noise.