EFFECT OF HIGH-ALTITUDE EXPOSURE IN THE ELDERLY - THE 10TH-MOUNTAIN-DIVISION STUDY

Background More than 5 million people/year over age 60 visit high alti tude, which may exacerbate underlying cardiac or pulmonary disease, We hypothesized that the elderly would exhibit an impaired functional ca pacity at altitude, with increased myocardial ischemia compared with s ea level (SL). Methods and Results Twenty veterans (68+/-3 years) were studied at (1) SL, (2) acute simulated altitude to 2500 m, and (3) af ter 5 days of acclimatization to 2500 m, With acute altitude, Pao(2) a nd oxyhemoglobin saturation decreased and pulmonary artery pressure in creased 43%, associated with sympathetic activation. Vo(2peak) decreas ed 12% acutely but normalized after acclimatization. The best predicto r of Vo(2peak) with acute altitude was Vo(2peak) at SL (r=.94). The do uble product that induced l-mm ST depression during exercise with acut e altitude was 5% less than SL but normalized after acclimatization. O ne patient with severe coronary disease sustained a myocardial infarct ion after an exercise test. Conclusions Moderate altitude exposure in the elderly is associated with hypoxemia, sympathetic activation, and pulmonary hypertension resulting in a reduced exercise capacity that i s predictable based on exercise performance at SL. Patients with coron ary artery disease who are well compensated at SL do well at moderate altitude, although acutely ischemia may be provoked at modestly lower myocardial and systemic work rates. The elderly acclimatize well with normalization of SL performance after 5 days. A prudent policy would b e for elderly Individuals, particularly those with coronary artery dis ease, to limit their activity during the first few days at altitude to allow this acclimatization process to occur.