Those living in the Alps are less likely to die of a heart attack or a stroke than those living in the valleys, a Zurich University study has found.
Even just being born in the mountains has a beneficial effect, according to researchers at the university's Institute of Social and Preventive Medicine.
"We could show that the risk of dying of a heart attack decreased by 22 per cent for each 1,000 metres of increase in altitude," David Fäh, the study's author, told swissinfo.ch.
"1,000 metres corresponds roughly to the altitude difference between the Swiss capital Bern and the mountain resort of Davos," he added.
For strokes, the risk decreased by 12 per cent per 1,000 metres.
Researchers looked at mortality from cardiovascular disease - heart attacks and strokes - in relationship to the altitude of the place of residence in 1990 and at birth for the 1.6 million people living in German-speaking Switzerland.
The idea was to gain a better overview of the effects of altitude on cardiovascular mortality, which until now has only been patchily investigated in other studies, with sometimes contrasting results.
The research, the first of its kind in Switzerland, was published earlier this week in Circulation, the journal of the American Heart Association.
For many, the mountains – home of clean air and soaring views that are good for the soul – have a healthy reputation. But Fäh said that it could not be determined exactly why altitude seemed to be better for hearts.
"We couldn't say why this was the case exactly... but we could show that a causal relationship was very likely," he explained.
The team of epidemiologists could, however, determine that the results were unlikely to be due to mountain dwellers having a healthier lifestyle than their valley counterparts. It did not appear to be the case that they smoked less or were less obese, for example.
"Our idea is that there is a direct impact of the effect of altitude on the body and there are also some climate influences," Fäh said.
"For instance, UV radiation, meaning sunlight exposure, is higher in the mountains and we know that this can improve the vitamin D production in the body which decreases the cardiovascular risk."
Being born at altitude seems to have an additional and independent benefit, it was found.
"If somebody was born 1,800 metres high in St Moritz in the Engadine [Valley] and then moved to Zurich, he keeps a part of the advantage with respect to cardiovascular mortality," said Fäh. "It appears there is a sustained effect of altitude on cardiovascular mortality."
It was not possible to say from the study how long would be needed in a high altitude place, for example after somebody moved there from a low altitude, before a beneficial effect on the heart was felt.
According to figures released last year, around 37 per cent of deaths in Switzerland were attributed to cardiovascular disease in 2004, making it one of the biggest killers in the country.
The Swiss rate is, however, low compared with most European countries.
Although some factors, such as diet, smoking and lack of exercise, are known to influence the development of heart disease, the role altitude plays has not yet been fully investigated. Previous studies, such as ones carried out in the United States and in Greece, have had limitations, said Fäh.
For example, other differences between the high and low attitude populations could not be taken into account.
"Switzerland offers a good setting because the homogeneity of the population in German-speaking Switzerland is high, meaning there are few differences with respect to ethnicity, socio-economic status, health behaviour or access to healthcare services between high and low regions," Fäh told swissinfo.ch.
"So we really have reason to believe that the effect comes from altitude and is not confounded by other differences which may occur within a country."
This problem would have been produced had the French- and Italian-speaking areas of Switzerland been included in the study.
"There are large cultural difference, for example, French-speaking Swiss drink alcohol more frequently than Swiss Germans and we know that alcohol may have a protective effect on cardiovascular mortality," said Fäh.
Another reason for exclusion of the Italian- and French-speaking parts was that climatic conditions differ between the north and south Alps.
"We limited it to German-speaking Switzerland because of that, but there are still 1.6 million people in the study."
Isobel Leybold-Johnson in Zurich, swissinfo.ch
The Zurich altitude study
The study was published in the Circulation journal on July 27:
Faeh D, Gutzwiller F, Bopp M, for the Swiss National Cohort Study Group. Lower mortality from coronary heart disease and stroke at higher altitudes in Switzerland. Circulation. 2009;120:495-501. doi: 10.1161/CIRCULATIONAHA.108.81925
It used Swiss mortality data from 1990-2000, socio-demographic information and places of birth and residence in 1990 gained from the Swiss National Cohort, a longitudinal census based record linkage study.
Further investigation will be necessary to elucidate protective factors potentially leading to decreased cardiovascular mortality at higher altitudes.
Cardiovascular disease is the leading cause of death among women and men in Europe. It is also a major cause of disability and of reduced quality of life.
The main, well-known risk factors for cardiovascular disease are tobacco use and raised blood pressure and blood cholesterol. These factors are directly related to individual lifestyle and eating habits as well as physical activity levels.
Other factors associated with cardiovascular disease include being overweight or obese, diabetes mellitus, excessive alcohol consumption and psychosocial stress.
In an international comparison of 20 countries for cardiovascular mortality for 2002 made by the World Health Organisation, Switzerland was in the lower quarter, along with neighbouring Italy and France. Japan was at the bottom. The top five included Germany, and was led by Estonia and Hungary. The United States was 6th and Scotland 8th.