Circadian preferences, oxidative stress and inflammatory cytokines in bipolar disorder: A community study

- Subjects with bipolar disorder and depression showed an evening preference and a greater alteration in biological rhythms.
- Cytokines and stress oxidative levels had no differences among subjects with bipolar disorders, depression and control group.
- Elevated levels of IL-6 and TBARS were found in subjects with evening preferences in bipolar disorder group.

ObjectiveTo assess circadian preference among a community sample of people with bipolar disorder, major depression and without any mood disorders. Secondly, we investigated the association of circadian preference with cytokines interleukin-6 (IL-6), interleukin-10 (IL-10) and, tumor necrosis factor alpha (TNF-α) and oxidative stress assessed by thiobarbituric acid reactive substances (TBARS), uric acid and Protein Carbonyl Content (PCC).MethodA cross-sectional study nested in a population-based sample. Caseness was confirmed with the Structured Clinical Interview for DSM-IV. A sample of 215 participants, in whom we measured circadian preferences, IL-6, IL-10, TNF-α, TBARS, uric acid, PCC. Biological rhythms were evaluated using the Biological Interview of Assessment in Neuropsychiatry.ResultsBipolar group presented a higher alteration in biological rhythms (40.40 ± 9.78) when compared with the major depression group (36.35 ± 9.18) and control group (27.61 ± 6.89) p < 0.001. Subjects with bipolar disorder who were active at night and had a day/night cycle reverse showed decreased levels of IL-6 (t, 44 = 2.096; p = 0.042), (t, 44 = 2.213; p = 0.032), respectively. In the bipolar disorder group subjects who presented day/night cycle reverse had lower TBARS levels (t, 41 = 2.612; p = 0.013). TNF-α were decreased in subjects more active at night with bipolar disorder.ConclusionLower serum levels of IL-6, TNF-α and TBARS were associated with evening preference in bipolar disorder group. These findings suggest that chronotype may alter the levels of interleukins and oxidative stress levels in bipolar and healthy subjects. A better understanding of the role of circadian preferences in levels of interleukins and oxidative stress are needed.