Sleeping position affects the hairline recession in male patients with androgenetic alopecia

Clinical observations indicate that some male patients with androgenic alopecia show varying degrees of hairline recession in the frontal and temporal regions on both sides, often with noticeable asymmetry between the left and right, which suggests a potential link to certain lifestyle habits. In this study, 161 male patients with androgenic alopecia were included, all exhibiting an "M"-shaped hairline. Patients' sleeping positions and combing directions were recorded and the areas of hairline recession in the frontal and temporal regions were calculated. Analysis of variance showed a significant difference in the ratio of the left and right receding hairline areas among patients with different sleeping positions (left lateral 1.19 ± 0.15 vs. right lateral 0.90 ± 0.10 vs. supine 1.00 ± 0.15 vs. no fixed position 1.00 ± 0.14, F = 24.84, p < 0.01). However, no significant difference in hairline recession was observed between patients who combed their hair to the left and those who combed to the right (p = 0.47). In conclusion, sleeping position may be an independent factor that influences the pattern of hairline recession of male patients with androgenic alopecia, particularly those with "M"-shaped hairlines, whereas combing direction appears to have no impact.