Altitude, life expectancy and mortality from ischaemic heart disease, stroke, COPD and cancers: national population-based analysis of US counties
- Majid Ezzati1,2,
- Mara E M Horwitz3,
- Deborah S K Thomas4,
- Ari B Friedman5,
- Robert Roach6,
- Timothy Clark7,
- Christopher J L Murray3,
- Benjamin Honigman6
- 1MRC-HPA Centre for Environment and Health, Imperial College, London, UK
- 2Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, London, UK
- 3Institute for Health Metrics and Evaluation, University of Washington, Seattle, Washington, USA
- 4Department of Geography and Environmental Sciences, University of Colorado Denver, Denver, Colorado, USA
- 5University of Pennsylvania, Philadelphia, Pennsylvania, USA
- 6Altitude Research Center and Department of Emergency Medicine, University of Colorado Denver School of Medicine, Aurora, Colorado, USA
- 7US Army Corps of Engineers, Engineering Research and Development Center, Topographic Engineering Center, Alexandria, Virginia, USA
- Correspondence to Dr Majid Ezzati, MRC-HPA Center for Environment and Health, Department of Epidemiology and Biostatistics, Imperial College London, St Mary's Campus, Norfolk Place, London W2 1PG, UK;
Contributors ME, DSKT, CJLM and BH designed the study. MEMH and ABF analysed county mortality, socio-demographic and solar radiation data; DSKT and TC analysed county elevation data. ME and CJLM designed the statistical analysis of the elevation–outcome relationship, and MEMH conducted the statistical analysis. ME and MEMH wrote the first draft of the paper with input from other authors. MEMH, ABF and ME had access to all data used in the study. ME is the guarantor for the study.
- Accepted 9 February 2011
- Published Online First 15 March 2011
Background There is a substantial variation in life expectancy across US counties, primarily owing to differentials in chronic diseases. The authors' aim was to examine the association of life expectancy and mortality from selected diseases with altitude.
Methods The authors used data from the National Elevation Dataset, National Center for Heath Statistics and US Census. The authors analysed the crude association of mean county altitude with life expectancy and mortality from ischaemic heart disease (IHD), stroke, chronic obstructive pulmonary disease (COPD) and cancers, and adjusted the associations for socio-demographic factors, migration, average annual solar radiation and cumulative exposure to smoking in multivariable regressions.
Results Counties above 1500 m had longer life expectancies than those within 100 m of sea level by 1.2–3.6 years for men and 0.5–2.5 years for women. The association between altitude and life expectancy became non-significant for women and non-significant or negative for men in multivariate analysis. After adjustment, altitude had a beneficial association with IHD mortality and harmful association with COPD, with a dose–response relationship. IHD mortality above 1000 m was 4–14 per 10 000 people lower than within 100 m of sea level; COPD mortality was higher by 3–4 per 10 000. The adjusted associations for stroke and cancers were not statistically significant.
Conclusions Living at higher altitude may have a protective effect on IHD and a harmful effect on COPD. At least in part due to these two opposing effects, living at higher altitude appears to have no net effect on life expectancy.
Funding The study was supported by the Centers for Disease Control and Prevention (CDC) through the Association of Schools of Public Health (ASPH) (Grant No U36/CCU300430-23), the Altitude Research Center and MRC-HPA Centre for Environmental and Health, Imperial College London.
Competing interests None.
Provenance and peer review Not commissioned; externally peer reviewed.