Impact of residence altitude on readmission in patients with heart failure.

Objective: Mountain districts normally have tougher geographic conditions than plain districts, which might worsen heart failure (HF) conditions in patients. Also, those places frequently are associated with social problems of ageing, underpopulation and fewer medical services, which might cause delay in detection of disease progression and require more admissions. We investigated the association of residence altitude with readmission in patients with HF. Methods: We followed 452 patients with HF to determine all-cause readmissions over a median of 1.1 years. The altitude of patient residences, population, proportion of the elderly and number of hospitals or clinics in a minor administrative district (Cho-Aza district) located at the residences were examined using data from the 2010 census and Google Maps. Results: All-cause readmissions were observed in 269 (60%) patients. The altitude of ≥200  m was significantly associated with readmissions (HR, 1.49; 95 % CI 1.12 to 1.96; p=0.006) after adjustment for physical and haemodynamic parameters, left ventricular ejection fraction, brain natriuretic peptide and components of the established score for predicting readmission for HF. Altitude was significantly associated with ageing, underpopulation, fewer hospitals or clinics and lower temperature (all p<0.01), with an increased tendency for readmission during the winter season; however, it was not associated with patient clinical parameters. Conclusions: High altitude residence may be an important predictor for readmission in patients with HF. This relationship may be confounded by unfavourable sociogeographic conditions at higher altitudes.