Patients' estimates of their sleep times: reliability and impact on diagnosis of obstructive sleep apnoea.

Background: Home polysomnography (PSG) is an alternative method for diagnosis of obstructive sleep apnoea (OSA). Some types 3 and 4 PSG do not monitor sleep and so rely on patients' estimation of total sleep time (TST).

Aim: To compare patients' subjective sleep duration estimation with objective measures in patients who underwent type 2 PSG for probable OSA.

Methods: A prospective clinical audit of 536 consecutive patients of one of the authors between 2006 and 2013. A standard questionnaire was completed by the patients the morning after the home PSG to record the time of lights being turned off and estimated time of sleep onset and offset. PSG was scored based on the guidelines of the American Academy of Sleep Medicine.

Results: Median estimated sleep latency (SL) was 20 min compared with 10 min for measured SL (P < 0.0001). There was also a significant difference between the estimated and measured sleep offset time (median difference = -1 min, P = 0.01). Estimated TST was significantly shorter than the measured TST (median difference = -18.5 min, P = 0.002). No factors have been identified to affect patients' accuracy of sleep perception. Only 2% of patients had a change in their diagnosis of OSA based on calculated apnoea-hypopnoea index.

Conclusions: Overall estimated TST in the patients with probable OSA was significantly shorter than measured with significant individual variability. Collectively, inaccurate sleep time estimation had not resulted in significant difference in the diagnosis of OSA.