Dr. Stephen Smagula Correlates Greater Sleep Fragmentation and Less Sustained/Sharply Segregated Resting and Active Periods in Strained Caregivers with Depression Severity

Depression is associated with disturbances to sleep and the 24-hour sleep-wake pattern, or rest-activity rhythm (RAR). However, there remains a need to identify the specific sleep/RAR correlates of depression symptom severity in population subgroups, such as strained dementia caregivers, who are at elevated risk for major depressive disorder. In a five-year study led by Dr. Smagula’s mentor, Martica Hall, PhD, Professor of Psychiatry, investigators assessed the cross-sectional associations of sleep/RARs with non-sleep depression symptom severity among 57 strained, older dementia caregivers currently without clinical depression who were caring for a live-in spouse. 

The investigators derived sleep measures from polysomnography and actigraphy and modelled RARs using a sigmoidally transformed cosine curve. They gauged non-sleep depression symptom severity using the Hamilton Depression Rating Scale with sleep items removed. Sleep-wake measures associated with greater depression symptom severity included more time awake after sleep onset, higher RAR middle level, relatively shorter active periods (alpha), earlier evening settling time, and less steep RARs.

Findings suggest that greater sleep fragmentation and less sustained/sharply segregated resting and active periods in strained caregivers correlate uniquely with depression symptom severity. This work was preliminary data supporting Dr. Smagula’s successful application for an NIMH-funded K01 award. This K01 is prospectively investigating whether these independent sleep-wake correlates of depression symptoms explain heightened depression risk in dementia caregivers, and how these sleep-wake markers affect brain health in aging caregivers.

While waiting for the prospective results, Dr. Smagula says, “Caregivers who are settling earlier have more depression symptoms and worse sleep, meaning it is possible that such caregivers could benefit from engaging in evening-time activities that build their sleep drive.” Longitudinal studies will tell whether RARs can help detect depression development before it occurs, or if RARs are indeed targets for preventing caregiver depression.

Rest-activity Rhythm and Sleep Characteristics Associated with Depression Symptom Severity in Strained Dementia Caregivers
Smagula S, Krafty R, Taylor B, Hall MH, Schulz R, Martire LM
Journal of Sleep Research, ePub ahead of print published online 2017, doi.org/10.1111/jsr.12549