Title: Reduced noise Impacts of Short-Term Aircraft Noise and Cardiovascular Outcomes (RISTANCO)
Funder: Department of Health and Social Care

Abstract: In areas affected by aircraft noise near major airports, relief periods of lower or absent aircraft noise are valued by residents whether in relation to deliberate flight path changes or weather variations especially wind direction. However, the impact of short-term changes in aircraft noise on physical health is unclear. Investigations, including from the HYENA study (Jarup, Environ Health Perspect 2008), have established associations between chronic exposure to aircraft noise and hypertension and with long-term average aircraft data and cardiovascular disease (Hansell, BMJ 2013; Vienneau Environ Res 2015). Short-term effects on cardiovascular outcomes have been little studied, in part due to lack of availability of relevant exposure data. However, recent experimental studies have documented short-term rises in blood pressure and cardiovascular risk markers in the blood in association with aircraft noise exposure during sleep (Schmidt F 2015) and short-term associations of road traffic noise with cardiovascular mortality (Walker ED, 2016, Tobias A, 2015). It is therefore possible that there are short-term as well as chronic effects of aircraft noise exposure on cardiovascular health, as is the case for particulate air pollution. This study proposes to utilise variability in night and daytime aircraft noise related to flight path trials, and operational and weather-related (e.g. easterly/westerly wind) changes in flight paths in the area around London Heathrow airport. This forms a ‘natural experiment’ to examine for short-term effects of reductions in aircraft noise on cardiovascular disease in the general population around London Heathrow airport affected by aircraft noise numbering >3 million (Hansell, BMJ 2013). We will use flight track movements 2011-15 to generate daily noise metrics for night-time and daytime noise and number of events. These will be used to examine potential associations between daily hospital admissions and mortality from cardiovascular disease in relation to variations in population exposures. Statistical analyses using a case-crossover approach (statistically equivalent to a time-series but able to take into account space as well as time variability) will compare noise exposure on the day of the event with 'control' days (e.g. past two days and following two days, same day in the fortnight either side). Analyses will take account of other factors that might influence cardiovascular disease on a day-to-day basis such as temperature, other meteorological factors and air pollution. Factors that might interact such as ethnicity and deprivation will also be investigated. Smoking habits do not change on a day to day basis so would not affect the analyses. Interaction terms in the statistical model will be used to determine whether areas with higher noise shows high daily variability have different risk estimates from those where noise levels are more constant. This will also be one of the first studies to examine short-term associations of aircraft noise with cardiovascular outcomes. The results will allow us to infer (i) whether interventions that reduce aircraft noise levels reduce cardiovascular disease outcomes in the short-term (ii) whether areas with relief periods show reduced risk of cardiovascular admissions with implications as to whether these should be regularly scheduled (respite periods).

Lay abstract: Aims: The aim of this study is to investigate whether day-to-day changes in aircraft noise levels affect risk of heart attack and stroke in the population living near airports and provide information on whether relief periods may have beneficial effects on cardiovascular disease. Background: There is good evidence that aircraft noise can affect quality of life, cause annoyance and disturb sleep. There are now a number of studies suggesting that long-term exposures may result in high blood pressure and potentially also impact on cardiovascular health. The mechanisms for this may include psychological stress and lack of restorative sleep, both of which impact on heart and cardiovascular health. Our previous study around London Heathrow airport published in the BMJ in 2013 found that higher long-term average aircraft noise exposures were associated with higher average risks of hospital admission and mortality for heart disease and stroke but the study did not look at short-term effects. A recent study has shown that exposure to aircraft noise at night results in transient increases in blood pressure the next morning and in cardiovascular risk markers in the blood. However, very few studies have looked at short-term effects of noise on cardiovascular disease events. To give confidence that analyses can actually detect what might be small increases in risk, such studies would need to include large numbers of people and detailed information on daily aircraft noise levels that is not readily available at present. Design and methods: This study will use sophisticated methods taking account of every aircraft flying into and leaving London Heathrow to estimate daily noise exposures for 2011-2015. These change on a day-to-day basis with wind direction (easterlies or westerlies) and through planned operational changes in flight plans. Noise estimates at place of residence will be linked with national hospital admission and mortality data. Statistical analyses will look for associations between aircraft noise and risk of a heart attack or stroke, taking into account other factors such as changes in temperature and air pollution that might also affect these risks. We will be able to examine whether reductions in noise exposure reduce risks and also whether there are differences between areas that are consistently noisy compared with those where noise levels vary. We will use different types of noise measures and look at noise at night as well as daytime. Patient and public involvement: We have discussed the proposed study design with members of the public involved with HACAN (Heathrow Association for Control of Aircraft Noise). They suggested that noisy events are more disturbing than general noise levels, so we will conduct analyses using a metric of number of noisy events in addition to analyses using average day and night noise levels. We will present and discuss study design and results with HACAN and other lay groups. Dissemination: We will present results at scientific meetings and as scientific journal papers. We will arrange meetings with local NGOs, local authorities near Heathrow and national organisations such as Environmental Protection UK. We will meet and discuss results with stakeholders including London Heathrow and other airport representatives and with Defra. Lay summary results will be posted on our website.

Research activity codes: 2.2 FACTORS RELATING TO PHYSICAL ENVIRONMENT
Health categories: CARDIOVASCULAR