Diurnal Rhythm Robustness in Individuals With PTSD and Insomnia and The Association With Sleep

Abstract

Posttraumatic stress disorder (PTSD) and insomnia are characterized by sleep disturbances and daytime functional impairments. Actigraphy metrics can quantify diurnal rhythms via interdaily stability, intradaily variability, relative amplitude, and sleep regularity. Here, we (a) compared diurnal rhythms in PTSD, insomnia, and healthy control samples using linear mixed modeling; (b) compared inter-individual variability of diurnal rhythms between groups using variance ratio tests; and (c) examined correlations between diurnal rhythms and sleep measures within the clinical samples. Participants (N = 98) wore wrist-activity monitors for one week and completed the Insomnia Severity Index and Pittsburgh Sleep Quality Index. Both clinical samples displayed significantly lower interdaily stability, relative amplitude, and sleep regularity compared with controls. Individuals with PTSD and insomnia did not differ on mean diurnal rhythm metrics. Both clinical samples showed more inter-individual variability in relative amplitude compared with controls, and the individuals with PTSD were distinguished from those with insomnia by greater inter-individual variability in interdaily stability and relative amplitude. Relative amplitude in the clinical samples was positively correlated with objective sleep efficiency and total sleep time. This is the first study to compare individuals with PTSD and insomnia on measures of diurnal rhythms, revealing those with PTSD and insomnia to have less robust and more variable diurnal rhythms compared with controls. Individuals with PTSD differed from those with insomnia in inter-individual variability of diurnal rest-activity stability and amplitude, highlighting this population as particularly heterogenous. Diurnal rhythm robustness might be considered an intervention target in insomnia and PTSD populations.

Trial registration: ClinicalTrials.gov NCT01009112.

Keywords: actigraphy; amplitude; diurnal; insomnia; posttraumatic stress disorder; regularity; sleep; stability; variability.

Conflict of interest statement

Conflict of Interest Statement: The author(s) have no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Figures

Figure 1.

Representative actograms of diurnal rhythms. Panel A represents an individual with insomnia (IS = .38, IV = 0.79, RA = .84, SRI = 75.82). Panel B represents an individual with PTSD (IS = .35, IV = 0.91, RA = .62, SRI = 77.65). Each row indicates 24-hours from mid-day to mid-day. Diary-reported rest intervals are the shaded sections, and activity counts per 60-second epoch are indicated by the height of each vertical line.

Figure 2.

Inter-individual variability of diurnal rhythm measures by diagnostic group. Means and standard deviations are indicated by the lines. Significant between group mean values, after controlling for demographics is indicated by: * p value < 0.05, two-tailed. ** p value < 0.001, two-tailed. Significant differences on inter-individual variability between groups, after controlling for demographics, is indicated by: # p value < 0.05, two-tailed. ## p value < 0.001, two-tailed.