# Impact of Sleep Apnea Treatment in Patients with Unexplained Syncope: The SINCOSAS Study

## TL;DR

Treating sleep apnea in patients with unexplained fainting episodes reduced fainting, improved heart rate patterns, and enhanced quality of life.

## Contribution

Demonstrates that sleep apnea treatment can reduce syncope recurrence and improve autonomic function in patients with unexplained syncope.

## Key findings

- Syncope episodes decreased from 62.6% to 16.2% after sleep apnea treatment.
- Heart rate variability measures like RR interval and RMSSD improved significantly.
- Quality of life scores on vitality and a visual analogue scale increased significantly.

## Abstract

Objectives: Unexplained syncope (US) persists despite extensive diagnostic evaluations, with autonomic dysfunction as a central mechanism. Sleep apnea (SA) may contribute through intermittent hypoxemia and autonomic imbalance. We evaluated the impact of SA treatment on syncope recurrence, nocturnal heart rate variability (HRV), and quality of life in patients with US. Methods: We conducted a prospective multicentre study in three hospitals in Galicia (Spain), including adults with US who underwent home respiratory polygraphy. SA was diagnosed according to guideline criteria, and treatment was prescribed when indicated (positive airway pressure therapy, positional therapy, and/or weight management). Symptoms, syncope burden, nocturnal heart rate variability derived from the ECG signal, and quality of life (SF-36 and a 0–100 visual analogue scale) were assessed at baseline and after 12 months. Results: Of 141 patients, 99 met treatment criteria, and 67 completed the 12-month follow-up. Mean age was 64.5 years; 59.6% were men; mean AHI was 25.9/h. After therapy, daytime sleepiness (Epworth score decreased from 8 to 5; p = 0.001), fatigue, nocturnal awakenings, and syncopal episodes decreased from 62.6% to 16.2%, 56.6% to 16.2%, and 3 to 0, respectively (all p < 0.001). HRV showed increased RR interval (p < 0.001) and RMSSD (p = 0.04). Quality of life improved in vitality (SF-36 vitality domain increased from 44 to 50; p = 0.02) and on the visual analogue scale (0–100: 50 to 70; p = 0.002). Conclusions: In this prospective cohort of patients with US and SA, therapy for SA was associated with fewer syncope recurrences, improvements in nocturnal respiratory indices, and selected heart rate variability measures, and better self-reported fatigue and vitality. Given the single-arm design and potential adherence and selection biases, these findings should be interpreted with caution and warrant confirmation in controlled studies.