Sleep alterations in individuals recently diagnosed with bipolar disorder across different mood stages

•Euthymic individuals with BD experience sleep impairments within 3 years after conversion from MDD to BD diagnosis.•Subjects recently diagnosed with BD during euthymia showed lower sleep efficiency and higher sleep disturbances as compared to MDD.•The differences in sleep quality observed between newly diagnosed euthymic BD and euthymic MDD could provide insights regarding prognosis, treatment, and the extent to which these individuals display significant subsyndromal symptomatology, even in the absence of a mood episode. : To assess the differences in sleep impairments in major depressive disorder (MDD) and individuals recently diagnosed with bipolar disorder (BD) across different mood stages. This is a cross-sectional study corresponding to the second wave of a prospective clinical cohort of a sample of outpatients. The first wave included subjects diagnosed with MDD aged 18 to 60 years. Averaging 3 years after the first phase (second wave), conversion from MDD to BD diagnosis was assessed using the Mini International Neuropsychiatric Interview. The total sample was divided into four groups: euthymic MDD, MDD in a current episode, euthymic BD, and BD in a current mood episode. The sleep alterations were assessed using the Pittsburgh Sleep Quality Index. The sample included 468 subjects (261 euthymic MDD, 149 MDD currently depressed, 16 euthymic BD, and 42 BDs currently in a (hypo)manic or depressive episode). Euthymic BD differed from euthymic MDD only in the domains of sleep efficiency and sleep disturbances, showing lower sleep efficiency (PR 4.91 [95%CI 1.94 – 12.42]) and higher sleep disturbances (PR 3.38 [95%CI 1.32 – 8.67]) in subjects recently diagnosed with BD during euthymia. These differences remained significant after adjusting for the potential confounding factors. The findings point out the relevance of regular sleep assessments in individuals recently diagnosed with BD, since the differences in sleep quality observed could provide insights regarding prognosis, treatment, and the extent to which these individuals display significant subsyndromal symptomatology, even in the absence of a mood episode.