Timing of dysregulation in rest-activity rhythm and depression symptom severity in dementia caregiversGraves, Jessica (2018) Timing of dysregulation in rest-activity rhythm and depression symptom severity in dementia caregivers. Master's Thesis, University of Pittsburgh. (Unpublished)
AbstractIntroduction: Several studies have shown differences in rest-activity rhythms (RARs) are associated with poor mental health outcomes, like depression. However, few studies have explored how the timing of these differences in RAR patterns influences subclinical depression, a known risk factor for developing future depression. The present study proposes three measures of activity to evaluate the effects of timing on subclinical depression symptom severity (non-sleep items from the Hamilton Rating Scale for Depression (HRSD)) in dementia caregivers (n=57). Methods: The three proposed measures, calculated within 4-hour time bins, include: absolute mean activity within each time period, standard deviation of mean activity across days in each time bin, and relative activity in each time bin. 4-hour time bins are defined based on proposed `Person-Time' (clock-time minus wake-up hour). Spearman correlations and linear regressions were used to assess the association between each measure at each time bin and depression, using age and gender as covariates. Group-based trajectory analysis was also used to identify clusters of activity trajectories, which were subsequently tested for associations with depression scores using Analysis of Covariance (ANCOVA). Results: Spearman correlations showed that 20 to 24 hours after waking, mean activity and relative activity were positively associated with depression score (rho = 0.37, P-value <0.01 and rho = 0.35, P-value = 0.01, respectively). Spearman correlations also revealed a significant negative association between relative activity and depression score (rho = -0.42, P-value <0.01) 12 to 16 hours after waking. Multiple regression models showed that at 20 to 24 hours after waking, both mean activity (beta = 0.96, beta P-value <0.01, model P-value = 0.007, adj. R^2 = 0.16) and relative activity (beta = 21.81, beta P-value <0.01, model P-value = 0.01, adj. R^2 = 0.15) were positively associated with depression score. Standard deviation of mean activity was not significantly associated with depression score across all regression models. Trajectory analyses identified two latent RAR types based on each of the three activity measures. ANCOVA of cluster assignments based on mean activity showed a significant association with depression score (F-value = 5.28, P-value = 0.03), controlling for age and sex. Conclusion: Results suggested that activity late in a patient's RAR is associated with increased subclinical depression severity in dementia caregivers. Public Health Significance: These analyses may help inform where in a patient's RAR an activity- or sleep-based interventions should be applied. Share
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