Background: Obstructive sleep apnea (OSA) and chronic insomnia frequently coexist, with 39 -58 of the OSA population suffering also from insomnia. This combination known as COMISA has scarcely been studied despite its health impact. The objectives of this study were to: i) characterize heart rate variability (HRV), a non-invasive indicator of autonomic nervous function, in people with COMISA, and ii) compare changes in HRV pre- to post-intervention in this population. 

Methods: Individuals with mild-to-moderate OSA (AHI: 5-30) and comorbid insomnia were recruited, assessed, and randomly assigned to either three weekly sessions of exercise training (Ex) or self-guided relaxation (R) for 8 weeks. HRV was measured from ECG recordings obtained at rest the morning after sleep assessments at baseline (N=6 Ex; N=8 R) and post-intervention (N=5 Ex; N=6 R). ECG was manually inspected and cleaned using an HRV analysis software (Mindware Technologies, USA). HRV indices included time domain measures (SDNN, RMSSD) and frequency domain measures (LF/HF, LF, HF). Descriptive statistics were obtained, and a two-way repeated-measures ANOVA was conducted.

Results: HRV outcomes generally fell within the normal expected range for healthy adults. No significant time-by-intervention interaction or main effect of intervention (exercise vs relaxation) was found. A significant main effect of time (pre to post) was observed for LF/HF (F(1,9) =8.710; p= 0.016) and LF (F(1,9) = 6.380; p= 0.032); both outcomes decreased in 8/11 participants, suggesting an improved HRV.

Conclusion: Individuals with COMISA are characterized with normal HRV when compared to normative values for healthy individuals. Nevertheless, exercise and relaxation training may improve certain HRV outcomes and preserve autonomic function in this population.