Letter by Eller et al Regarding Article, “Lower Mortality from Coronary Heart Disease and Stroke at Higher Altitudes in Switzerland”
To the Editor:
We read with great interest the article titled “Lower Mortality from Coronary Heart Disease and Stroke at Higher Altitudes in Switzerland” by Faeh et al.1 In the large Swiss National Cohort, the authors convincingly show a lower mortality from coronary heart disease (−22% per 1000 m) and stroke (−12% per 1000 m) with increasing altitude. They conclude that this effect may be due to factors related to climate, although there was no adjustment for classic risk factors of atherosclerosis such as diabetes mellitus.
Interestingly, there is a clear regional variability in the incidence of diabetes mellitus type 2 and its sequel, end-stage renal failure, in the neighboring Alpine state of Austria, where mountainous areas such as Tyrol have a significantly lower incidence of type 2 diabetes mellitus in comparison with lowlands.2 Like German Switzerland, Austria has an ethnically homogenous population, universal access to health care, and places of residence allocated between 200 and 2000 m with only minimal changes in geographic latitude.
Clinician investigators and article reviewers would greatly benefit from knowing whether there is a similar regional variability in the incidence of type 2 diabetes mellitus in Switzerland, inasmuch as diabetes mellitus constitutes a crucial risk factor for atherosclerosis,3 and may explain on its own the different mortality for coronary heart disease and stroke in highlanders and lowlanders in Switzerland.
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.
Wimmer F, Oberaigner W, Kramer R, Mayer G. Regional variability in the incidence of end-stage renal disease: an epidemiological approach. Nephrol Dial Transplant. 2003; 18: 1562–1567.