Nasal variation in relation to high‐altitude adaptations among Tibetans and Andeans

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Abstract
Objectives: High‐altitude (>2500 m) populations face several pressures, including hypoxia and cold‐dry air, resulting in greater respiratory demand to obtain more oxygen and condition inspired air. While cardiovascular and pulmonary adaptations to high‐altitude hypoxia have been extensively studied, adaptations of upper‐respiratory structures, e.g., nasal cavity, remain untested. This study investigates whether nasal morphology presents adaptations to hypoxic (larger noses) and/or cold‐dry (tall/narrow noses) conditions among high‐altitude samples.Methods: CT scans of two high‐ and four low‐altitude samples from diverse climates were collected (n = 130): high‐altitude Tibetans and Peruvians; low‐altitude Peruvians, Southern Chinese (temperate), Mongolian‐Buriats (cold‐dry), and Southeast Asians (hot‐wet). Facial and nasal distances were calculated from 3D landmarks placed on digitally‐modeled crania. Temperature, precipitation, and barometric pressure data were also obtained.Results: Principal components analysis and analyses of variance primarily indicate size‐related differences among the cold‐dry (Mongolian‐Buriats) and hot‐wet (Southeast Asians) adapted groups. Two‐block partial least squares (PLS) analysis show weak relationships between size‐standardized nasal dimensions and environmental variables. However, among PLS1 (85.90% of covariance), Tibetans display relatively larger nasal cavities related to lower temperatures and barometric pressure; regression analyses also indicate high‐altitude Tibetans possess relatively larger internal nasal breadths and heights for their facial size.Conclusions: Overall, nasal differences relate to climate among the cold‐dry and hot‐wet groups. Specific nasal adaptations were not identified among either Peruvian group, perhaps due to their relatively recent migration history and population structure. However, high‐altitude Tibetans seem to exhibit a compromise in nasal morphology, serving in increased oxygen uptake, and air‐conditioning processes.

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