Q&As relating to the SAHSU study "Aircraft noise and cardiovascular disease near London Heathrow Airport"

Study published in the BMJ October 12th 2013 (http://www.bmj.com/cgi/doi/10.1136/bmj.f5432 )


What does the study show?

The study looked at the risk of hospital admissions and deaths from stroke, heart disease and circulatory disease in neighbourhoods exposed to aircraft noise related to Heathrow airport. The highest levels of aircraft noise were associated with increased risks of stroke, coronary heart disease, and cardiovascular disease for both hospital admissions and mortality in those areas.  Risks were increased even after allowing for other factors known to affect disease risk such as deprivation, ethnicity, smoking, road traffic noise and air pollution.


What size of effects are we talking about?

There were excess risks of around 10-20% in areas with the highest levels of aircraft noise compared with the lowest levels.


What were the highest levels of aircraft noise looked at in this study?

The highest category of daytime noise was an annual average of >63 dB and the highest level of night-time noise was an annual average of >55 dB.


How loud is 55db or 63dB?

The noise levels are averages of events over time (when aircraft are flying overhead plus the periods in-between) so it is not possible to give an exact equivalent sound.


How many people are exposed to high levels of aircraft noise?

In the study, which used 2001 aircraft noise data, 2% or fewer of the study population lived in areas exposed to the highest categories. This was around 70,000 individuals for daytime aircraft noise >63 dB, and around 80,000 individuals for night- time aircraft noise >55 dB.


SAHSU does not hold more recent aircraft noise data, but published reports from Heathrow suggest that aircraft noise exposure has been falling over time.


Why adjust for ethnicity?

South Asian ethnicity is associated with increased risks of heart disease and Black ethnicity with increased risk of stroke.  Some neighbourhoods near Heathrow have a high percentage of people with South Asian ethnicity so would be expected to have high rates of heart disease, regardless of any noise exposures. Therefore we had to take ethnicity into account in our analyses. In particular, we found that adjustment for South Asian ethnicity reduced the observed association between heart disease hospital admissions and aircraft noise.


The study relates to health effects in 2001-2005.  Is it relevant now?

Yes.  The study looks at the association between noise levels and hospital admissions and mortality. We see no reason why this should not be relevant now. However, the number of people exposed to high levels of aircraft noise has fallen since 2001.


How would aircraft noise make you more likely to have a stroke or heart attack?

Unexpected loud noise activates the nervous system producing a startle reaction, which increases blood pressure and heart rate in the short term.  Loud noise may also cause annoyance and annoyance may also increase blood pressure and heart rate in the short term. While it is possible that this may also increase risk of high blood pressure in the long term, studies to date relating to environmental noise have not been conclusive.


Should we be worried about health effects of aircraft noise in London?

We consider our work raises the possibility that aircraft noise may be a potential contributing factor to stroke, heart and circulatory disease, but the exact role that noise exposure may play in ill-health is not well understood.


I live in an area with high levels of aircraft noise – do I have an increased risk of stroke or heart disease?

The role that noise exposure may play in ill-health is not well understood and needs further study.  Our study examined the average risks in areas, but this is not the same as the risk for an individual as individual circumstances will differ.  Well-established risk factors for stroke, heart and cardiovascular disease are lifestyle factors such as smoking, obesity, low levels of exercise and an unhealthy diet and medical conditions such as diabetes, high blood pressure and high cholesterol (especially if untreated). These factors are likely to be the most important determinants of disease risk.


We would advise anyone concerned about their risk of stroke or heart disease to discuss with their family doctor.


Should I get double glazing or soundproofing to reduce my risk of stroke or heart disease?

This was not investigated in the current study.  We are not aware of any published studies that have looked at a relationship between noise reduction measures such as double glazing or soundproofing and disease risks.


How does this study compare with other studies?

There are very few studies looking at associations with between aircraft noise and stroke, heart disease or circulatory disease and findings are not fully consistent. Two large studies in Vancouver and Denmark didn’t find associations but three other studies have, including a study on 89 airports in the USA published at the same time as this study in the BMJ (http://www.bmj.com/cgi/doi/10.1136/bmj.f5561).


Associations between aircraft noise and long-standing high blood pressure (a risk factor for heart disease and stroke) have been seen in the small number of studies conducted to date.


There are more studies on road traffic noise where associations have been seen for heart disease, stroke and hypertension. Adjustment for exposure to road traffic noise in the present study did not affect the associations with aircraft noise.


What about air pollution from Heathrow?

The study did not look at air pollution specifically related to Heathrow.  However, we did investigate whether air pollution levels in the London area affected our estimates for aircraft noise and found they did not.


Was night-time noise worse than daytime noise?

The results suggested that associations between risk of both hospital admissions and mortality tended to be higher for night-time noise than daytime noise at equivalent levels.  However, more research is needed to confirm this. Areas with higher levels of night-time noise were those with higher daytime noise so we can’t be confident that there is a true difference.


The study refers to both coronary heart disease and cardiovascular disease. What is the difference?

Cardiovascular disease refers to conditions affecting the circulatory system, which includes heart disease and stroke and other conditions affecting the blood vessels including blood clots. Coronary heart disease includes angina and heart attack. It is called ischemic heart disease in the USA.


Is the effect of different types of noise additive?

Most research treats different type of noise such as road, railway, aircraft and community noise as separate exposures because the characteristics and quality of the noise differ. We found that road noise exposure did not affect the associations we saw with aircraft noise.


How does this work contribute to the current work of the Airports Commission about possible need for additional airport hub capacity in the UK and where it might be located?

The results raise questions about potential long-term health impacts of aircraft noise. Our study contributes to the body of evidence that the commission will need to consider.


Who funded the study?

The work of the Small Area Health Statistics Unit (SAHSU) is funded by the MRC (Medical Research Council) and PHE (Public Health England) as part of the MRC-PHE Centre for Environment and Health at Imperial College London and King’s College London. The study also had financial support from the European Union funded project the European Network for Noise and Health.



Further references

Paper details

Hansell AL, Blangiardo M, Fortunato L, Floud S, de Hoogh K, Fecht D, Ghosh RE, Laszlo HE, Pearson C, Beale L, Beevers S, Gulliver J, Best N, Richardson S, Elliott P. Aircraft noise and cardiovascular disease near London Heathrow Airport



The UK Small Area Health Statistics Unit (SAHSU)



The MRC-PHE Centre for Environment and Health at Imperial College London and King’s College London http://environment-health.ac.uk/


Advice about preventing heart disease and stroke

Further information can be found on these NHS websites www.nhs.uk/Conditions/Coronary-heart-disease/Pages/Prevention.aspx and www.nhs.uk/Conditions/Stroke/Pages/Prevention.aspx and from the British Heart Foundation www.bhf.org.uk/heart-health/prevention.aspx and the Stroke Association www.stroke.org.uk/about/preventing-stroke.


WHO documents about environmental noise 


Civil Aviation Authority reports on noise exposure contours around Heathrow Airport

The most recent report is “Noise Exposure Contours for Heathrow Airport 2011” www.gov.uk/government/uploads/system/uploads/attachment_data/file/3933/heathrow-2011-report.pdf published by the Civil Aviation Authority in 2012