Physiological and Sleep Profiles in Insomnia, OSA and COMISA: A Comparative Study in Portugal and Spain.

Insomnia and obstructive sleep apnea (OSA) are common sleep disorders that often co-occur as comorbid insomnia and sleep apnea (COMISA), worsening health outcomes. This study characterized and compared the physiological and sleep profiles of insomnia, OSA and COMISA in population-based datasets from Portugal (n = 147) and Spain (n = 264), excluding patients with cardiovascular disease. Classification followed clinical guidelines, and analyses included polysomnography and heart rate variability (HRV) data. Conventional HRV metrics in the time and frequency domains, along with condition-specific frequency bands (BWMS, BWOSA, BWCOMISA, BWRes) were compared alongside demographic and clinical variables. The Portuguese and Spanish datasets differed significantly in gender distribution, daytime sleepiness, sleep efficiency and apnea-hypopnea index (AHI), with Spanish patients showing a higher severity of AHI and a predominantly male composition. COMISA patients were older, had higher BMI, and showed a hypopnea-dominant respiratory profile in both datasets. Classical HRV indices did not differ significantly between groups, although trends suggested decreased parasympathetic activity in OSA. Condition-specific bands were largely non-discriminative in Portugal, while BWOSA emerged as a significant marker of respiratory burden in Spain. When the populations were analysed jointly, age and obesity remained significant risk factors and COMISA maintained its hypopnea-dominant profile. The combined dataset revealed significant differences in several HRV features. OSA and COMISA patients exhibited a higher cardiovascular burden and autonomic imbalance (lower HF, higher LF/HF and LFn), while condition-specific bands all showed discriminatory power across groups. BWOSA may represent a useful spectral biomarker for OSA, although population and methodological factors strongly influence discriminative power.