RESUMEN
In bipolar disorders, abnormalities of sleep patterns and of circadian rhythms of activity are observed during mood episodes, but also persist during euthymia. Shared vulnerabilities between mood disorders and abnormalities of sleep patterns and circadian rhythms of activity have been suggested. This exploratory study investigated the association between polygenic risk scores for bipolar disorder and major depressive disorder, actigraphy estimates of sleep patterns, and circadian rhythms of activity in a sample of 62 euthymic individuals with bipolar disorder. The polygenic risk score - bipolar disorder and polygenic risk score - major depressive disorder were calculated for three stringent thresholds of significance. Data reduction was applied to aggregate actigraphy measures into dimensions using principal component analysis. A higher polygenic risk score - major depressive disorder was associated with more fragmented sleep, while a higher polygenic risk score - bipolar disorder was associated with a later peak of circadian rhythms of activity. These results remained significant after adjustment for age, sex, bipolar disorder subtype, body mass index, current depressive symptoms, current tobacco use, and medications prescribed at inclusion, but not after correction for multiple testing. In conclusion, the genetic vulnerabilities to major depression and to bipolar disorder might be associated with different abnormalities of sleep patterns and circadian rhythms of activity. The results should be replicated in larger and independent samples.
RESUMEN
BACKGROUND: Bipolar Disorder (BD) is associated with alterations of circadian rhythms of activity (CRA). Experimental research suggests that lithium (Li) modifies CRA, but this has been rarely explored in BD using actigraphy. METHODS: The sample comprised 88 euthymic BD-I cases with 3 weeks of actigraphy. We used a Principal Component Analysis (PCA) to generate CRA dimensions. We then used linear regression analyses to compare these dimensions between groups of individuals defined according to prescribed mood stabilizers: Li monotherapy ("Li" group, n = 28), anticonvulsant or atypical antipsychotic monotherapy ("AC or AAP" group, n = 27) or combined treatments ("Li+AC or Li+AAP" group, n = 33). Analyses were adjusted for potential confounders (gender, age, body mass index, depressive symptoms, co-prescribed benzodiazepines and antidepressants, smoking status and past alcohol use disorder). RESULTS: The PCA identified two dimensions: "robust CRA" (high amplitude and interdaily stability, with low intradaily variability) and "late chronotype". Univariate analyses showed higher scores for "robust CRA" in the "Li" versus the "AC or AAP" (p = 0.021) or "Li+AC or Li+AAP" groups (p = 0.047). These findings remained significant after adjustments (respectively p = 0.010 and p = 0.019). Post-hoc analyses suggested lower variability, higher stability and higher amplitude of CRA in the "Li" group. Medication groups were similar for the "late chronotype" dimension (p = 0.92). CONCLUSIONS: This actigraphy study is the first to show more favorable CRA in BD-I individuals receiving a Li monotherapy when compared with those receiving other classes or combinations of mood stabilizers. Replications in larger samples are required. Prospective studies are also warranted to elucidate whether the introduction of Li or other mood stabilizers might influence CRA in BD-I.
RESUMEN
INTRODUCTION: Disturbances in sleep and circadian rhythmicity (CR) are frequent in individuals with bipolar disorders (BD). Very few studies explored the associations between psychotropic medications and these disturbances in euthymic BD. Therefore, we aimed at exploring the associations between several classes of medications (lithium, sedative/non-sedative Atypical Antipsychotics (AAP), anticonvulsants, antidepressants, benzodiazepines) and sleep disturbances and CR dimensions in a sample of euthymic individuals with BD. METHODS: We included euthymic adults with BD type 1 or 2 assessed with 21 days of actimetry. We used a Principal Component Analysis (PCA) of sleep and CR estimates to generate dimensions to be studied in association with the current use of psychotropic medications, with adjustments for potential confounding factors. RESULTS: We included individuals with BD-1 (n = 116) or BD-2 (n = 37). The PCA led to four dimensions of sleep and CR estimates. Benzodiazepines were associated with better sleep quality (pcorrected = 0.032). Aripiprazole was associated with less robust CR (pcorrected = 0.016), but with earlier peak of activity patterns (pcorrected = 0.020). Sedative AAPs were associated with better sleep quality, which was no longer significant after correction. We found no association between lithium or anticonvulsants and CR. LIMITATIONS: The cross-sectional design and the possible non-representativeness of the sample were limitations of our study. CONCLUSIONS: In euthymic individuals with BD, benzodiazepines may have a positive effect on sleep quality, while aripiprazole may have mixed effects on CR (less robust but with earlier peak of activity patterns). No association with lithium or anticonvulsants observed. Further studies are warranted to replicate and extend these results.