Aging at high altitudes and the risk of chronic mountain sickness

Abstract

Clinical records of healthy high altitude (HA) (4300 m [14 100 ft]; n=2875) and sea level (SL) (n=2899) miners were examined for vital capacities (VC), body weights (W), heights (H), and hemoglobin (Hb) concentrations in different age groups. In the HA population, excessive erythrocytosis (EE) was defined as Hb ≥ 21.3 g dl⁻¹; i.e., the mean Hb in the 20–29 age group plus 2 sd. This level of Hb is one of the parameters above which clinical chronic mountain sickness (CMS) becomes apparent. We found a smooth increasing prevalence of EE with age: 6.8% at age 20–29 to 33.7% at age 60–69. Height corrected VC (VC/H) decreases 3.0% between ages 20–29 and 60–69 years in SL miners and 26.5% in HA for the same age interval. In the latter, the pronounced decrease in VC/H is seen both in miners with EE (30.6%) and in those with physiological erythrocytosis (PE, 22.4%). SL miners have significantly higher W/H ratios than do HA ones. This index steadily increases with age at SL. At HA, however, miners with EE and PE show a drop in their weights after ages 40–49 years. In addition, EE miners have higher W/H ratios than do PE ones between ages 40–59 years. We suggest that increasing Hb and diminishing VC with age at HA do not represent the so-called physiological adaptation. On the contrary, these may be risk factors for the development of CMS with age among HA Andean populations.