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People who live close to airports and are exposed to loud aircraft sound levels could be up to four times more likely to suffer a heart attack or stroke, say scientists.

The study, led by (UCL) researchers, looked at detailed heart imaging data from 3,635 people who lived close to four major British airports.

The research team compared the hearts of those who lived in areas with higher aircraft noise with those who lived in lower aircraft noise areas.

They found that those who lived in areas with higher than recommended aircraft noise levels had stiffer and thicker heart muscles that contracted and expanded less easily and were less efficient at pumping blood around the body.

The researchers said it was especially the case for people exposed to higher aircraft noise at night, potentially due to factors such as impaired sleep and the fact that people are more likely to be at home at night and therefore exposed to the noise.

The team found in separate analyses of people not exposed to aircraft noise, that these types of heart abnormalities could result in two- to four-fold increased risks of a major cardiac event such as a heart attack, life-threatening heart rhythms, or stroke.

Senior author Dr. Gaby Captur, of UCL and consultant cardiologist at the Royal Free Hospital, London, said: 鈥淥ur study is observational so we cannot say with certainty that high levels of aircraft noise caused these differences in heart structure and function.

鈥淗owever, our findings add to a growing body of evidence that aircraft noise can adversely affect heart health and our health more generally.

鈥淐oncerted efforts from government and industry are needed to reduce our exposure to aircraft noise and mitigate its impact on the health of millions of people who live close to airports or under flight paths.鈥�

Professor Anna Hansell, of the , said: 鈥淲e are concerned that the type of abnormalities we saw with night-time aircraft noise might result in increased risk of heart problems and stroke.

"Aircraft noise at night has been shown to affect sleep quality and this may be an important factor affecting health.

鈥淭he role of noise on heart health is currently under investigation."

The researchers said that as well as affecting sleep, environmental noise can also trigger stress responses and lead to an over-activation of the sympathetic nervous system, causing blood pressure to rise, arteries to constrict or dilate, and slower digestion.

It can also cause the release of the stress hormone cortisol, which can increase appetite and cause weight gain.

Scientists say aircraft noise may be more annoying than road or rail noise because of louder but intermittent noisy events and the unpredictability of the sound which makes it difficult to get used to.

It is already known that exposure to high levels of aircraft noise is linked to higher blood pressure and obesity.

In the new study, both factors were found to account for a "significant" portion of the link between aircraft noise and differences in heart structure and function.

First author Dr Cristian Topriceanu, of UCL, said: 鈥淏etween a quarter and half of the link was attributed to a higher body mass index among participants exposed to higher levels of aircraft noise, while between 9% to 36% of the link was attributed to these participants having higher blood pressure.

鈥淥ther factors that could be triggered by the stress response to aircraft noise include impaired sleep, inflammation, and atherosclerosis.鈥�

For the new study, published in the (JACC), the research team analyzed data from the UK Biobank of 3,635 participants who had detailed magnetic resonance imaging (MRI) of the heart and who lived near Heathrow, Gatwick, Birmingham or Manchester airports.

They used estimates of aircraft noise level for every 100 square meters within those areas.

Higher aircraft noise was defined as over 50 decibels on average during the day and 45 decibels on average during the night, from 11 p.m. to 7 a.m.

That is louder than the aircraft noise limits of 45 decibels on average during the day and 40 decibels on average at night recommended by the (WHO).

Heart MRIs were done at least three years after the estimates of aircraft noise in the local area.

The researchers found that participants who stayed in a higher aircraft noise area, had about 10% to 20% worse heart structure and function than their counterparts in those areas who moved away.

The researchers then looked at a separate sample of 21,360 people who had detailed MRI scans of the heart as part of the study to investigate how heart abnormalities comparable to those linked to higher aircraft noise might affect the risk of a major adverse cardiac event.

They concluded that a hypothetical individual with these heart abnormalities may have up to four times the risk of an event such as a heart attack, abnormal heart rhythm, or stroke.

Earlier research led by the University of Leicester estimated that about 5% of adults in England were exposed to aircraft noise exceeding 50 decibels either during the day or night.

Professor James Leiper, associate medical director at the British Heart Foundation (BHF), said: 鈥淔or most of us, a plane is seen as a ticket to some well-deserved rest and relaxation.

"But this innovative study reveals the potential invisible impact for those living close to some of our biggest travel hubs."

He added: 鈥淲hile observational studies like this can鈥檛 prove cause and effect, these findings add to previous research showing the damaging impact of noise pollution on our heart health.

"Further research will be needed to investigate the longer-term effects of aircraft noise on the health of those with the highest exposure.鈥�