Arterial oxygenation during sleep in Sherpa highlanders has been relatively unexplored. This study was designed to investigate arterial oxygen saturation (Sa(O(2))) and pulse rate (PR) during sleep in 61 Sherpa (29 men, 32 women) who had lived at 3,450-3,850 m in Nepal, from adolescence through old age, and to estimate the relative effects of aging on arterial oxygenation during sleep. The mean Sa(O(2)) during sleep (mSa(O(2))) was found to decrease with age, and to negatively correlate with the mean PR during sleep. About one-third of subjects (n=19) exhibited a periodical fluctuation of Sa(O(2)) during sleep. The subjects who exhibited a periodical fluctuation of Sa(O(2)) during sleep were older and their mSa(O(2)) were lower compared with those who did not exhibit a periodical fluctuation of Sa(O(2)), and the cycle of periodical fluctuation got longer with advancing years. These findings indicated that sleep desaturation occurs in high altitude residents with advancing years.