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Sleep disturbance in mild cognitive impairment: differential effects of current and remitted depression

Naismith SL, Rogers NL, Lewis SJG, Diamond K, Terpening Z, Norrie L, Hickie IB. Sleep disturbance in mild cognitive impairment: differential effects of current and remitted depression. Objective: Although patients with mild cognitive impairment (MCI) commonly report sleep disturbance, the extent to which depressive symptoms contribute to this relationship is unclear. This study sought to delineate the contribution of current and remitted major depression (MD) to sleep disturbance in MCI. Methods: Seventy-seven patients meeting criteria for MCI (mean age = 66.6 ± 8.8 years) were grouped according to those with no history of depression (MCI, n = 33), those meeting criteria for current MD [mild cognitive impairment and meeting criteria for current major depression (DEP-C), n = 14] and those with remitted MD [mild cognitive impairment and remitted major depression (DEP-R), n = 30]. Additionally, 17 healthy controls (CON) participated. Sleep was patient-rated using the Pittsburgh Sleep Quality Index and included assessment of sleep quality, duration, efficiency, disturbances, medications, sleep onset latency and daytime dysfunction. Depression severity was clinician-rated using the Hamilton Depression Rating Scale. Results: Overall sleep disturbance was significantly greater in the DEP-C and DEP-R groups in comparison to the CON and MCI groups (p < 0.001). Only 12% of CON reported sleep disturbance, compared to 30% of MCI, 63% of DEP-R and 86% of DEP-C. Sub-scale analysis showed that the sleep disturbance in depressive groups was most evident across the domains of sleep quality, sleep efficiency, sleep latency and daytime dysfunction. Conclusion: Sleep disturbance in MCI is strongly associated with a current or past diagnosis of MD. The finding that sleep complaints are still prominent in those with remitted depression, suggests that ‘trait' markers exist that may reflect underlying neurobiological changes within the sleep–wake system.