Sleep / Wake Disorders
Intra-Individual Sleep Variability: Associations with Anxiety and Depression
David L. Yap, M.A.
Graduate Student
Hunter College, City University of New York
New York, New York
Evelyn Behar, Ph.D.
Associate Professor
Hunter College, City University of New York
New York, New York
Anxiety and depression are related to sleep quality both cross-sectionally and longitudinally (Alvaro, Roberts, & Harris, 2013). Although most existing studies have examined these relationships by comparing group means on sleep measures, a growing body of evidence suggests that levels of intra-individual variability may be higher than between-groups variability (e.g., Hilten et al., 1993; Knutson, Rathouz, Yan, Liu, & Lauderdale, 2007; Mezick et al., 2009). Furthermore, most studies have used measures of psychopathology that capture general negative affect as opposed to specific levels of anxiety or depression. For example, Mezick and colleagues (2009) found a significant positive relationship between mood and variability in sleep duration and fragmentation, but measured mood using a combined measure of anxiety and depression (CES-D + STAI-T). Lemola, Ledermann, and Friedman (2013) extended these finding by measuring anxiety and depression independently using the Mood and Anxiety Symptom Questionnaire (MASQ; Watson, Clark, & Tellegen, 1988), which measures anhedonic depression and anxious arousal orthogonally. They found that variability of total sleep time was a significant positive predictor of both anxiety and depression symptoms. However, they examined intra-individual variability of only one sleep index (total sleep time), although variability of other sleep indices (e.g., time to bed, sleep onset latency, wake after sleep onset, time to rise, sleep efficiency, sleep quality) may be important to examine given their differential susceptibility to behavioral and environmental influences (Bei, Wiley, Trinder, & Manber, 2016). Furthermore, both Mezick et al. (2009) and Lemola et al. (2013) recruited samples of middle-aged and older adults (i.e., 35-85 years of age); however, a systematic review of the correlates of daily sleep variability found younger age to be associated with more variable sleep timing (Bei et al., 2016).
The current study will examine the relationship between multiple indices of intra-individual sleep variability and orthogonally measured anxiety and depression symptoms in a large (N = 182) nationally representative sample of adults aged 18-65 years. Data come from a longitudinal study using experience sampling to measure daily levels of anxiety, depression, and daily sleep indices. At baseline, we administered the Pittsburgh Sleep Quality Index (PSQI; Buysse et al., 1989) and the MASQ, which yields orthogonal measures of Anxious Arousal (specific to anxiety) and Anhedonic Depression (specific to depression). Each day for seven days, participants completed a morning sleep diary. We calculated intra-individual variability in daily sleep indices (total sleep time, time to bed, sleep onset latency, number of awakenings, time to rise, sleep efficiency, and sleep quality). Data collection is complete and will be analyzed in the Spring 2022. We will use multilevel modeling to determine the proportion of total variance attributable to intra-individual differences and between-individual differences in each of these sleep indices, with MASQ Anxious Arousal and Anhedonic Depression scores as potential differential person-level predictors of intra-individual variability on these indices.