Patient-predicted sleep position vs. HST data: a tendency to underestimate supine sleep.

Subjects in this study frequently underestimated their proportion of supine sleep compared to values measured in an HST. Because of the increased supine sleep they exhibited, the severity of their OSA was often greater in the test than it would have been had the subjects slept as they predicted. Sleep physicians should take into account the tendency of people to underestimate supine sleep. If patients with positional sleep apnea assert that they "always sleep laterally" when at home, they may be underestimating their true night-by-night OSA disease burden.