O068 Vascular and Autonomic Function in Comorbid Insomnia and Sleep Apnoea

Abstract Comorbid insomnia and sleep apnoea (COMISA) is a common sleep disorder and may be associated with increased cardiovascular risk. This study aimed to compare polysomnography-derived biomarkers of cardiovascular risk in patients with COMISA, obstructive sleep apnoea (OSA) only, insomnia only, and without OSA or insomnia. Patients were identified from the Sydney Sleep Biobank database. Insomnia was defined as a positive test on the Insomnia Symptom Questionnaire (self-report of poor sleep and daytime impairment at least three times per week for four weeks). COMISA was defined as having insomnia and an apnoea-hypopnoea index >5 events/h. Heart rate variability (HRV) during stage N2 sleep and pulse wave amplitude drop (PWAD) parameters were derived from the electrocardiograms and plethysmography signals of polysomnograms, and compared between groups. To date 471 patients (median[IQR] age: 50[37, 62] years; 62% males) have been analysed. Forty-two percent of patients had OSA only, 22% had insomnia only, 23% percent had COMISA and 14% did not have OSA or insomnia. Patients with COMISA had lower HRV measures (SDNN, P=0.0218; Total Power, P=0.046; pNN50%, P=0.044; absolute low frequency power, LF, P=0.0034). After adjusting for age, sex and BMI, these metrics were not significant (P >0.05). PWAD frequency and duration were similar between groups (P >0.05). These preliminary data indicate patients with COMISA have altered cardiovascular autonomic function specifically reduced parasympathetic modulation indicated by lower pNN50%, Total Power and LF. This finding supports previous work demonstrating elevated cardiovascular risk in patients with COMISA, although age, sex, and BMI may be potential mediators.