STUDY OBJECTIVES
Since subjective sleep duration (SSD) is considered to be longer than objective sleep duration (OSD), results of SSD minus OSD (SSD-OSD) might always be thought to be positive. Some recent reports showed different results but exact results have not been obtained. The difference between SSD and OSD may change according to OSD. We investigated this difference and its association with sleep-disordered breathing (SDB) or nonrestorative sleep (NRS).
METHODS
This cross-sectional study evaluated 6908 community residents in Nagahama city, Japan. SSD was determined by self-administered questionnaire. OSD was measured by wrist actigraphy and sleep diary. SDB was assessed according to the 3% oxygen desaturation index adjusted for OSD.
RESULTS
Worthy of notice was that SSD was shorter than OSD longer than 6.98 hours in all participants, 7.36 hours in males and 6.80 hours in females. However, SSD was longer than OSD (mean±SD: 6.49±1.07 vs 6.01±0.96, P <0.001) overall, as SSD is considered to be longer than OSD. In patients with SDB, the difference between SSD-OSD was greater when OSD was shorter. The difference also depended on SDB severity. The degree of positivity between OSD and SSD was a significant factor in NRS (odds ratio: 2.691, P <0.001).
CONCLUSIONS
When OSD was slightly <7 (6.98) hours, participants reported or perceived SSD>OSD. When OSD was >6.98 hours, participants reported or perceived SSD<OSD. Patients with SDB reported longer SSD than OSD according to severity of SDB. Evaluating SSD, OSD and their difference may be useful for managing sleep disturbances including NRS.