Obstructive sleep apnoea is not a risk factor for incident hospitalised depression: a historical cohort study.

We evaluated whether obstructive sleep apnoea (OSA) was related to the incidence of hospitalisation for depression, a robust end-point that is unlikely to result from misdiagnosis.All adults referred with suspected OSA who underwent a diagnostic sleep study at a large urban academic hospital between 1994 and 2010 and were linked to provincial health administrative data between 1991 and 2015 were included. Cox regression analysis was used to investigate the association between OSA symptoms and severity and incident hospitalised depression, the primary outcome.Over a median follow-up of 9.7 years, 136 (1.3%) out of 10 149 participants were hospitalised for depression. A significant crude effect of OSA symptoms (waking unrefreshed and impact on memory and concentration) on hospitalised depression became nonsignificant after controlling for confounders. Apnoea-hypopnoea index was not significantly associated with the outcome: adjusted hazard ratio (33 versus 6 events·h-1) 1.13 (95% CI 0.91-1.40). Factors associated with hospitalised depression were female sex, younger age, use of hypnotics, alcoholism and unemployment.In a large clinical cohort with suspected OSA, controlling for confounders, OSA symptoms and severity were not related to the risk of hospitalisation for depression, suggesting that previously reported links between OSA and depression may be due to overlapping diagnostic criteria. However, our findings cannot exclude a potential link between OSA and milder depression.