Per cent oxygen saturation of arterial haemoglobin levels (SaO2), a measure of hypoxemia has been analysed in the permanent residents of Ladakh. The population recognized as high-altitude controls (HAC) and high-altitudemonks (HAM), resided at the same altitude of 3600 m but differed in their routines. SaO2 was measured with a Finger-Pulse Oximeter. The HAM had 3.08% higher SaO2 (P<0.001) compared to the HAC, with mean SaO2 of 91.8°6.1% and 89.0°2.6%, respectively. Furthermore, the younger HAM also revealed an elevation of 4.55% SaO2 than the HAC of identical age (P<0.001). The HAM, who are less hypoxemic than their counterparts are physically more active, which may be a selective advantage in the extreme environment of higher altitudes
