RESUMEN
BACKGROUND: Many studies have reported specific adaptations to high altitude, but few studies have focused on physiological variations in high-altitude adaptation in Andean highlanders. This study aimed to investigate the relationships between SpO2 and related factors, including individual variations and sex differences, in Andean highlanders. METHODS: The participants were community-dwelling people in La Paz, Bolivia, aged 20 years and over (age range 20-34 years). A total of 50 men and 50 women participated in this study. Height, weight, SpO2, hemoglobin concentration, finger temperature, heart rate, and blood pressure were measured. Information about lifestyle was also obtained by interview. RESULTS: There were individual variations of SpO2 both in men (mean 89.9%, range 84.0-95.0%) and women (mean 91.0%, range 84.0-96.0%). On Student's t test, men had significantly lower heart rate (p = 0.046) and SpO2 (p = 0.030) than women. On the other hand, men had significantly higher SBP (p < 0.001), hemoglobin (p < 0.001), and finger temperature (p = 0.004). In men, multiple stepwise regression analysis showed that a higher SpO2 was correlated with a lower heart rate (ß = - 0.089, p = 0.007) and a higher finger temperature (ß = 0.308, p = 0.030) (r2 for model = 0.18). In women, a higher SpO2 was significantly correlated with a higher finger temperature (ß = 0.391, p = 0.015) (r2 for model = 0.12). A higher SpO2 was related to a higher finger temperature (ß = 0.286, p = 0.014) and a lower heart rate (ß = - 0.052, p = 0.029) in all participants (r2 for model = 0.21). Residual analysis showed that individual SpO2 values were randomly plotted. CONCLUSION: Random plots of SpO2 on residual analysis indicated that these variations were random error, such as biological variation. A higher SpO2 was related to a lower heart rate and finger temperature in men, but a higher SpO2 was related to finger temperature in women. These results suggest that there are individual variations and sex differences in the hemodynamic responses of high-altitude adaptation in Andean highlanders.