Brain structure affects link between sleep disturbance, depressive symptoms in shift workers

Alterations in gray matter (GM) structure affect the impact of shift work on depressive symptoms, a recent study has found.

Researchers enrolled 20 shift-working nurses (mean age, 28.6±3.2 years) from whom structural magnetic resonance imaging (sMRI) data were collected. Sleep disturbance and depressive symptoms were assessed using the Pittsburgh Sleep Quality Index (PSQI) and the Zung Self-Rating Depression Scale, respectively. A parallel group of 19 day-working nurses (mean age, 30.8±4.0 years) was included as a comparator.

The mean PSQI score in the shift-working group was 7.1±1.8, as opposed to only 4.4±1.8 in day-workers. The percentage of participants with PSQI score >5, suggesting significant sleep disturbance, was almost twice that in the shift-work group (72 percent vs 31 percent). ZSDS scores were likewise higher in the shift-workers (43.1±6.4 vs 35.3±4.9).

Greater sleep disturbance correlated significantly with more severe depressive symptoms (p=0.0021). However, adjusting for inter-individual differences in GM volume revealed important effects.

Adjusting for the left post central gyrus (p=0.06) sand superior temporal gyrus (p=0.1227) attenuated the interaction between sleep disturbance and depressive symptoms. “That is, the intervening role of GM volume in the relationship between sleep disturbance and depressive symptom could be supposed for the two brain regions,” researchers explained.

Formal tests for the mediation hypothesis confirmed a significant indirect effect of both the left post central gyrus (p=0.0427) and the superior temporal gyrus (p=0.0118).