Daytime symptoms in primary insomnia: a prospective analysis using ecological momentary assessment

Abstract

Objectives: To prospectively characterize and compare daytime symptoms in primary insomnia (PI) and good sleeper control (GSC) subjects using ecological momentary assessment; to examine relationships between daytime symptom factors, retrospective psychological and sleep reports, and concurrent sleep diary reports.

Methods: Subjects included 47 PI and 18 GSC. Retrospective self-reports of daytime and sleep symptoms were collected. Daytime symptoms and sleep diary information were then collected for 1 week on hand-held computers. The Daytime Insomnia Symptom Scale (DISS) consisted of 19 visual analog scales completed four times per day. Factors for the DISS were derived using functional principal components analysis. Nonparametric tests were used to contrast DISS, retrospective symptom ratings, and sleep diary results in PI and GSC subjects, and to examine relationships among them.

Results: Four principal components were identified for the DISS: Alert Cognition, Negative Mood, Positive Mood, and Sleepiness/Fatigue. PI scored significantly worse than GSC on all four factors (p<0.0003 for each). Among PI subjects DISS scales and retrospective psychological symptoms were related to each other in plausible ways. DISS factors were also related to self-report measures of sleep, whereas retrospective psychological symptom measures were not.

Conclusions: Daytime symptom factors of alertness, positive and negative mood, and sleepiness/fatigue, collected with ecological momentary assessment, showed impairment in PI versus GSC. DISS factors showed stronger relationships to retrospective sleep symptoms and concurrent sleep diary reports than retrospective psychological symptoms. The diurnal pattern of symptoms may inform studies of the pathophysiology and treatment outcome of insomnia.

Figure 1. Functional Principal Components from the Daytime Symptoms in Insomnia (DISS) Scale

Group mean data for functional principal components of the Daytime Insomnia Symptom Scale (DISS). Values represent fitted standardized factor scale scores for each group. Because these represent standardized scale scores, the y-axis scales do not have specific units. Higher scores indicate a greater level of the construct for each scale (i.e., higher level of Alert Cognition, more Negative Mood, more Positive Mood, greater Sleepiness/ Fatigue). Group differences for each functional principal component was statistically significant at p < 0.001, indicating a different levels and time courses between insomnia (dashed line) and control (solid line) groups.