Pittsburgh and Epworth sleep scale items: accuracy of ratings across different reporting periods.

This study examined the ecological validity of sleep experience reports across different lengths of reporting periods. The accuracy of item responses on the Pittsburgh Sleep Quality Index (PSQI) and Epworth Sleepiness Scale (ESS) across 3-, 7-, and 28-day reporting periods was examined in relation to electronic daily item ratings. Primary care clinic patients (N = 119) were recruited, and were not required to have sleep problems to participate. Analyses found few differences in item scores when electronic daily ratings were compared with recall ratings, regardless of the length of the reporting period. However, within-subjects analyses indicated low levels of accuracy in recall of sleep items for specific days in the last week. Thus, for the purpose of between-subject comparisons, patients generally can provide accurate recall of sleep experiences; studies requiring finer-grained analysis across time and within-subjects require daily diary methodology.