Altitude-Induced Sleep Apnea Is Highly Dependent on Ethnic Background (Sherpa Vs. Tamang).

Heiniger, Grégory, Simon Walbaum, Claudio Sartori, Alban Lovis, Marco Sazzini, Andrew Wellman, and Raphael Heinzer. Altitude-Induced Sleep Apnea Is Highly Dependent on Ethnic Background (Sherpa Vs. Tamang). . 23:165-172, 2022. High altitude-induced hypocapnic alkalosis generates central sleep apnea (CSA). In Nepal, two ethnic groups live at medium-to-high altitude: Tamangs originate from low-altitude Tibeto-Burman populations, whereas Sherpas descend from high-altitude Tibetans. To compare apnea severity at low and high altitude between Sherpas and Tamangs. Polygraphy recordings, including airflow and oxygen saturation, were performed in Nepal at "low" (2,030 m) and "high" (4,380 m) altitudes. Resting ventilation () and mixed-exhaled CO (FCO) were also measured at the same altitudes. Differences in apnea-hypopnea index (AHI), oxygen desaturation index (ODI), and % of nocturnal periodic breathing (NPB) at the two altitudes were compared between ethnicities. Twenty Sherpas and 20 Tamangs were included (males, median [interquartile range] age: 24.5 [21.5-27.8] years vs. 26.0 [21.5-39.8] years, body mass index: 23.9 [22.1-26.1] kg/m vs. 25.21 [20.6-27.6] kg/m). Compared with Tamangs, Sherpas showed a lower increase in AHI (+7.5 [2.6-17.2]/h vs. +31.5 [18.2-57.3]/h,  < 0.001), ODI (+13.8 [5.5-28.2]/h vs. +42.0 [22.6-77.6]/h,  < 0.001), and NPB proportion (+0.9 [0-3.5]% vs. +12.8 [3.1-27.4]%,  < 0.001) from low to high altitude. Resting was higher in Sherpas versus Tamangs at both low (8.45 [6.89-10.70] l/min vs. 6.3 [4.9-8.3] l/min,  = 0.005) and high (9.7 [8.5-11] l/min vs. 8.74 [7.39-9.73] l/min,  = 0.020) altitudes, whereas the mean ± standard deviation FCO decrease between low and high altitude was greater in Tamangs versus Sherpas (-0.50% ± 0.44% vs. -0.80% ± 0.33%,  < 0.023). Overall, altitude-adapted Sherpas showed a 3.2-times smaller increase in sleep-disordered breathing between low and high altitude compared with Tamangs, and higher ventilation and a smaller drop in FCO at high altitude. These data suggest that genetic differences in breathing control can be protective against CSA.