Predictors and patterns of insomnia symptoms in OSA before and after PAP therapy.

Objective: Identify factors that predict improvement versus persistence of insomnia symptoms following treatment of obstructive sleep apnea (OSA) with positive airway pressure (PAP) therapy.

Methods: Archival data from 68 PAP-treated sleep apnea patients aged 25-83 were analyzed using nonparametric tests and stepwise regression to assess the relationships between insomnia symptoms, multiple OSA variables, and PAP use over time.

Results: Pretreatment insomnia symptom severity (ISS; b = -0.72, p < 0.001), PAP average use (b = -0.01, p = 0.01) and respiratory disturbance index (RDI; b = -0.02, p = 0.03) predict change in insomnia following PAP therapy. Forty-five percent (24/53) of the subjects with moderate to severe insomnia at pretreatment reported no/mild symptoms after PAP therapy and were considered improved. Improved subjects had lower pretreatment ISS (p < 0.001), higher RDI (p = 0.01), and higher average PAP use (p < 0.035) than subjects with persistent insomnia. Number of medications and comorbidities were similar between improved and persistent groups. New onset of insomnia symptoms occurred in 13% (2/15) of the patients with no/mild pretreatment insomnia.

Conclusions: Although ISS declines following PAP treatment, 55% of OSA patients have persistent moderate to severe symptoms despite treatment. More severe OSA is linked to higher likelihood of insomnia improvement and the effect of PAP therapy on insomnia may be mediated by OSA severity. Persistent insomnia is unrelated to medication use or comorbidities and may represent an independent, self-sustaining disorder requiring targeted intervention.