The aim of this cross-sectional study was to assess the health status of subjects weekly commuting between sea level and 3550-m altitude for at least 12 yr (average 22.1 +/- 5.8). We studied 50 healthy army men (aged 48.7 +/- 2.0) working 4 days in Putre at 3550-m altitude, with 3 days rest at sea level (SL) at Arica, Chile. Blood pressure, heart rate, Sa(O(2) ), and altitude symptoms (AMS score and sleep status) were measured at altitude (days 1, 2, and 4) and at SL (days 1, 2, and 3). Hematological parameters, lipid profile, renal function, and echocardiography were performed at SL on day 1. The results showed signs of acute exposure to hypoxia (tachycardia, high blood pressure, low Sa(O(2) )), AMS symptoms, and sleep disturbances on day 1, which rapidly decreased on day 2. In addition, echocardiographic findings showed pulmonary hypertension (PAPm > 25 mmHg, RV and RA enlargement) in 2 subjects (4%), a PAPm > 20 mmHg in 14%, and a right ventricle thickness >40 mm in 12%. Hematocrit (45 +/- 2.7) and hemoglobin (15 +/- 1.0) were elevated, but lower than in permanent residents. There was a remarkably high triglyceride level (238 +/- 162) and a mild decrease of glomerular filtration rate (34% under 90 mL/min and 8% under 80 mL/min of creatinine clearance). In conclusion, in these preliminary results, in chronic intermittent hypoxia exposure even over longer periods, most subjects still show symptoms of acute altitude illnesses, but a faster recovery. Findings in triglycerides, in the pulmonary circulation and in renal function, are also a matter of concern.

To determine the changes in blood pressure (BP) and related variables in sea-level young adults with chronic exposure to high altitude, a longitudinal study was performed in male army recruits (n = 346; age 17.9 +/- 0.1 yr; BMI, 22.5 +/- 0.3 kg/m(2)) first exposed to 3550-m altitude for 12 months. Fifty male recruits (age 17.8 +/- 0.6 and BMI 22.6 +/- 0.3 kg/m(2)) never exposed to altitude were used as controls. A sustained higher mean diastolic BP (DBP) (82.1 +/- 1.0 mmHg at month 3; 81.3 +/- 0.9 mmHg at month 12) was observed, compared to first exposure and the control group (p < 0.001). The BP values were always higher than those of the sea-level control group (systolic blood pressure (SBP) 109 +/- 2.3 and DBP 67.4 +/- 0.8; p < 0.001), and a large proportion of subjects steadily presented overoptimal values for either systolic BP (SBP) (64%) or DBP (77%) and hypertensive DBP values (40%). The higher DBP was associated with lower Sao(2) (OR = 0.919; p < 0.05). In addition, the acute mountain sickness (AMS) score showed a slight decrease during re-exposure (3.9 +/- 0.3 vs.3.4 +/- 0.3; p < 0.001) and an inverse association to the before-descending Sao(2) at month 3 (OR = 0.906, p < 0.01). These data suggest that BP stabilization can take longer than currently thought and that each parameter has a different profile of change. Further, a sustained high DBP should be a matter of epidemiological concern and emphasizes the need for BP monitoring among young lowlanders exposed to high altitude.

The aim of this epidemiological study was to determinate the effects on hematological and lipid profile in a young group of newcomers to altitude after being exposed chronically for 8 months to 3550 m (n = 50), age 17.8 +/- 0.7; and not overweight, BMI 22.9 +/- 0.5). Readings taken at altitude on day 1 and on month 8 were hematocrit (Hct, %), hemoglobin (Hb, g/dL), Sa(O(2)), total leukocyte and subset count (mm(3), %), and lipid profile (mg/dL). The same measurements were taken in a comparative group (CG) at sea level (SL). At altitude, elevations of Hct (44.6 +/- 0.4; 51.2 +/- 0.4) and Hb (15.5 +/- 0.1; 17.3 +/- 0.1) were seen (p < 0.001) and none with Hb >/= 21 g/dL. No correlation was observed between Hb and Sa(O(2)), r = 0.11, p > 0.05. Total leukocyte count showed no changes (6037 +/- 74; 6002 +/- 43), but a relative neutropenia (55.2 + -1.5; 50.6 + -1.3) and lymphocytosis (34.2 + 1; 42.4 + 1, p < 0.001) between periods were found and also when compared to SL. Also, an inverse relationship between Sa(O(2)) and total leukocytes on month 8 (r = 0.46; r(2) = 0.204), suggesting a probable representation of a hypoxia effect. Total cholesterol (153.8 +/- 4.5; 157.3 +/- 5.1; p, ns) showed no changes, but a mild decrease of LDL-cholesterol (88.4 +/- 3.3; 81.0 +/- 3.9; p < 0.05), and a rise in triglycerides (121.6 +/- 10.9; 178.8 +/- 11.7; p < 0.001) was found. Changes observed in leukocytes subset count and triglycerides could suggest a contributory role of hypoxic conditions, raising some future epidemiological concerns regarding immune system and fatty acid behaviour at altitude.