Why does Living at Higher Altitude Influence Death Rates for Selected Diseases and Conditions? An Ecologic Study Involving US Counties

Abstract

Objective: Higher altitude living has been associated with lower death rates for specific causes. This study will measure the association between altitude and selected causes of death and consider the effect other natural environmental factors have on these associations.

Methods: An ecologic study design involving 3,108 counties was used. Environmental variables included altitude and average daily sunlight, maximum air temperature, PM2.5, and precipitation. Age-adjusted mortality rates were considered for several causes of death.

Results: Counties with higher altitude have lower mortality rates for all causes, heart disease, cerebrovascular disease, tobacco-related cancer, non-tobacco-related cancer, and Alzheimer’s disease, and higher for suicide and accidents. Diabetes and pneumonia/influenza are not associated with altitude. Counties at ≥ 2500 meters compared with < 500 meters have 6.05% higher sunlight, 30.47% lower air temperature, 55.53% lower PM2.5, and 49.50% lower precipitation. County-level mean mortality rates were 35.86% lower for all causes, 43.16% lower for heart disease, 35.67% lower for cerebrovascular disease, 51.47% lower for tobacco-related cancer, 25.14% lower for non-tobacco-related cancer, and 39.13% lower for Alzheimer’s disease, and 93.89% higher for suicide. For accidents, the mean mortality rate was 30.97% higher through 2000-2499 meters, but the rates declined thereafter. Mean mortality rates are almost the same in the highest and lowest altitude groups for pneumonia/influenza.

Conclusion: In adjusted models accounting for the environmental variables, altitude, average daily maximum air temperature, PM2.5, and precipitation positively correlate with each of the causes of death considered, whereas average daily sunlight negatively correlates with the causes of death.