Quantifying the sources of discrepancy between total recording time and total sleep time in home sleep apnea testing: insights from home-based polysomnography.

Study objectives: To quantify the contribution of sleep onset latency (SOL), wake after sleep onset (WASO), and wake after sleep offset (WASF) in the discrepancy between total recording time (TRT) and total sleep time (TST) in home-based polysomnography (PSG) using patient-activated and deactivated monitoring devices.

Methods: This observational study enrolled patients with a high pretest probability of obstructive sleep apnea (OSA) who underwent unattended home-based PSG. We measured the duration of SOL, WASO, and WASF to quantify the discrepancy between TRT and TST. TRT was defined as the interval from device activation to deactivation by the patients. SOL represented the time from device activation to the first epoch of any sleep, WASO was the total amount of time spent awake after the sleep onset epoch until the last epoch of any sleep, and WASF was defined as the time from the last epoch of any sleep until the patient-initiated device deactivation. We also assessed differences in apnea-hypopnea index (AHI) between home-based PSG and type 3 sleep studies by reanalyzing home-based PSG recordings as simulated type 3 studies after omitting type 2 signals.

Results: A total of 78 patients were included in the study. The mean TRT exceeded the mean TST by 19%, with TRT at 457±78 min and TST at 383±68 min. The mean difference between TRT and TST was 74±53 min, attributed to SOL (30%), WASO (45%), and WASF (25%). There was considerable variability in the difference between TRT and TST among study participants, ranging from as little as 14 minutes to as much as 233 minutes. The mean AHI in simulated type 3 studies (41±29) was, on average, 23% lower than the mean AHI recorded in home-based PSG (53±30, P <.001).

Conclusions: There was significant variability in the gap between TRT and TST among patients with a high pretest probability of OSA undergoing unattended home-based PSG. WASO was identified as the largest contributor to this discrepancy, with notable contributions from SOL and WASF. Additionally, simulated type 3 studies underestimated the true AHI compared to type 2 studies.