Assessing Ecogeographic Variation in the Nasal Passages Utilizing 3D Semilandmarks

Purpose: Prior research has shown strong statistical relationships between geographically-patterned variation in nasal skeletal morphology and global climatic conditions. Specifically, the nasal skeletons of individuals indigenous to cold-dry environments tend to be longer, taller, and especially narrower, than those from hot-humid environments. As the nose heats and humidifies inspired air, this morphological patterning is believed to reflect the specific air-conditioning demands of different climates. However, while it is widely assumed the morphology of the nasal skeleton accurately reflects that of the functional (soft-tissue) nasal passages, the existence of ecogeographic variation in the three-dimensional (3D) nasal soft tissues has yet to be empirically demonstrated. Thus, this study investigates 3D shape variation in decongested soft-tissue nasal passages of individuals of European (EA) and African (AA) descent (n=15). Methods: Using 3D Slicer and Avizo, a total of 260 semi-landmarks were collected from the decongested nasal passages of each individual. General Procrustes Analysis (GPA) was then used to align the semilandmark configurations and a Principal Component Analysis (PCA) was subsequently performed using the Geomorph package in R. Results: PC1 (20.2%) largely contrasts EA individuals with positive PC1 scores (relatively narrower nasal passages) from AA individuals with negative PC1 scores (relatively wider nasal passages). Conclusions: These results generally conform to morphological expectations, suggesting a concordance between skeletal and decongested soft-tissue nasal anatomy. This study thus provides the impetus for future research investigating the relationship between variation in nasal soft-tissue anatomy and air-conditioning physiology.