Increased urinary IgM excretion in patients with obstructive sleep apnea

Background: Obstructive sleep apnea (OSA)-related intermittent hypoxemia may contribute to renal endothelial injury. Evidence on urinary immunoglobulin M (IgM-uria) in OSA is limited. We evaluated associations between OSA severity and IgM-uria and albuminuria in non-diabetic and diabetic patients. Methods: Cross-sectional study of 124 adults undergoing overnight polysomnography at a tertiary sleep clinic. Morning urine IgM and albumin were measured and normalized to creatinine. Multivariable linear regression models adjusted for age, sex, smoking, body mass index, and hypertension were fitted and interactions with diabetes status were tested. Results: Among non-diabetic participants (n = 98), a 1 SD decrease in mean SpO₂ was associated with a 0.65 SD increase in urinary IgM-uria and a 0.50 SD increase in albuminuria (both p < 0.001). A 1 SD increase in oxygen desaturation index was associated with 0.29 SD and 0.33 SD increases in IgM-uria (p = 0.014) and albuminuria (p = 0.006), respectively. A 1 SD increase in apnea–hypopnea index was associated with 0.24 SD and 0.22 SD increases in IgM-uria (p = 0.034) and albuminuria (p = 0.043), respectively. These associations were not significant among patients with diabetes (n = 26). Conclusions: Urinary IgM and albumin were associated with OSA severity in non-diabetic individuals, suggesting they could serve as inexpensive, non-invasive biomarkers of glomerular injury in sleep apnea. Longitudinal studies are warranted to assess reversibility with OSA treatment.