Associations of nonrestorative sleep with insomnia, depression, and daytime function.

Study Objectives: Nonrestorative sleep (NRS) complaints are common but associations with insomnia, daytime function or depressive symptoms are not well-established. This study aims to (1) describe insomnia related symptoms and sleep quality in those with NRS compared to those with no NRS; (2) identify the independent associations between NRS, insomnia severity, and depression; and (3) identify the association between NRS and daytime function independent of insomnia severity and depression.

Design: Cross sectional survey of enrollees at a health plan in the Midwestern United States.

Measurement: Respondents were surveyed about the presence and frequency of NRS complaints, depression, insomnia severity and related symptoms. Multivariate regression was used to examine the study's three research aims.

Participants: Study sample consisted of 541 subjects with NRS and 717 who reported never experiencing any NRS symptoms.

Results: We found a statistically significant interaction between NRS and total sleep duration such that the association between sleep duration and sleep quality was attenuated in those with NRS compared to those without NRS (b=-0.26, SE=0.07, p<0.0001). In multivariate analysis, subthreshold, moderate and severe insomnia were associated with NRS (OR [95%CI]=5.93 [4.24-8.31], 9.22 [6.15-13.83] and 6.10 [3.34-11.14], respectively). NRS was independently associated with daytime physical function, cognitive function and emotional function OR [95%CI]=2.21 [1.59-3.08], 1.90 [1.37-2.64] and 1.71 [1.23-2.36], respectively.

Conclusion: NRS is a complex concept that should be further defined and studied in the larger context of sleep quality, other insomnia related symptoms, daytime function and depression.