People who live in mountainous areas have better heart health than lowland dwellers, researchers have suggested.
Mountain living 'may be good for your heart'
The University of Athens Medical School team monitored 1,150 Greek people for 15 years.
The Journal of Epidemiology and Community Health found fewer deaths in total, and particularly from heart disease, among those in the highlands.
But British experts warned high altitudes could be dangerous for people who already had heart disease.
Residents of Arahova, in the mountainous Sterea Hellas region (950m above sea level), and Zevgolatio and Aidonia in the plains of the Peloponnesus region took part in a general health survey in 1981.
Information on gender, age, weight, smoking habit, blood pressure, and alcohol consumption, were recorded. Blood samples were also taken. Researchers returned to the villages in 1996.
Men in the villages made their living by farming and keeping animals, while the women tended to look after the home and family.
In Greece, deaths from heart disease are among the lowest of any developed country, a factor which could be largely due to the Mediterranean diet most people eat.
Both men and women living in the mountain village appeared to be at higher risk of coronary heart disease than people living in the lowland area, with higher rates of circulating blood fats and higher blood pressure.
However, by 1996, there had been a total of 133 deaths among the 566 people living in the mountains, and 157 deaths among those living on the plains.
Coronary heart disease caused the deaths of 11 men in the highland and 23 in lowland areas, and 16 among women in the highlands compared to 17 in the lowlands.
The researchers, led by Dr Nikis Baibas, said that since blood fats and blood pressure were higher among the mountain residents, "other 'protective' factors", especially among men, must come into play
Writing in the Journal of Epidemiology and Community Health, they said living at moderately high altitude produced long term physiological changes in the body to enable it to cope with lower levels of oxygen (hypoxia), and that this, combined with the exertion required to walk uphill regularly on rugged terrain, could give the heart a better work-out.
They add: "Increased physical activity under conditions of moderate hypoxia among mountain residents could explain these findings".
But Belinda Linden, Head of Medical Information at the British Heart Foundation, said the Greek researchers had not taken activity levels into account as part of the study.
She added: "Another major benefit for protection against CHD is a diet high in fruit and vegetables and oily fish, but the researchers admit that they did not gather information about the participants' diet.
"Due to these shortcomings in the design of the study, we cannot be sure that the results are robust."
Ms Linden said: "Although there could be some benefit from gradually increasing activity levels at higher altitudes, caution is needed.
"Activity at high altitude can cause exertion to be more difficult, due to the shortage of oxygen.
"Most healthy people can cope with this, but if you have heart disease or lung disease, reduced oxygen levels can cause extreme breathlessness, and these people should be cautious even at moderate altitude."
Jim Milledge, a mountain health expert said: "It is surprising that the modest altitude was enough to have a protective effect.
"There is little evidence around about the effect of altitude on heart health. But what there is suggests it could have a protective effect."