Background: There are limited data on the association between obstructive sleep apnea (OSA), which is characterized by intermittent hypoxia, and male-pattern baldness (MPB). Low blood iron levels are reportedly associated with hypoxia and hair loss. This study explored a possible link among OSA, iron status, and MPB. Methods: Polysomnography (PSG) and hair assessments were conducted in a cross-sectional study including 932 men aged 46–76 years. OSA was defined as an apnea-hypopnea index ≥5 by PSG evaluation and MPB as scales from IV to VII according to the Norwood-Hamilton scale classification. Serum transferrin saturation (TSA) levels were assessed. Results: A total of 224 men (24%) were identified as MPB cases and 495 men (53%) as having OSA. After considering potential risk factors, OSA and other sleep-related variables were not associated with MPB. In joint analysis of OSA and family history of hair loss, men with these two factors showed a sevenfold higher multivariate odds ratio (95% confidence interval: 3.70, 12.56) for MPB than those without both of them (P < 0.05 for the interaction between OSA and family history of hair loss). TSA levels were significantly associated with MPB and OSA. OSA cases without MPB as well as MPB cases showed lower TSA levels than those with neither OSA nor MPB (P < 0.05). Conclusions: These findings suggest that OSA may be a risk factor for MPB in men who have a family history of hair loss and that low serum TSA levels associated with hypoxia may be involved in a pathway linking OSA and MPB.
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