Age or age of onset: which is the best criterion to classify late-life depression?

In late-life depression (LLD), several differences between patients whose first episode is reported after age 65 (late-onset depression, LOD) and those with early-onset depression (EOD) might reflect the effects of brain ageing. To test this hypothesis, we analysed the impact of current age and age at illness onset on a number of clinical and cognitive manifestations in 438 outpatients with major depressive disorder aged >60 years, treated with venlafaxine for 12 weeks. When compared to the EOD group, patients with LOD were older (P < 0.00001) and associated with lower depression severity (P = 0.0029), lower global cognitive functioning [Mini-Mental State Examination (MMSE): P = 0.0001; Repeatable Battery for the Assessment of Neuropsychological Status: immediate memory, P = 0.0009, and delayed memory, P < 0.00001; Delis-Kaplan Executive Function System measuring executive functions: Trail-Making Test (TMT) - P = 0.0004 and Colour-Word Interference Test, Inhibition - P = 0.0063], and more dyskinesias (Abnormal Involuntary Movement Scale: P = 0.0006). After controlling for its interactions with age of onset, current age was inversely correlated with Montgomery angstrom sberg Depression Rating Scale scores at baseline (P < 0.00001) and week 12 (P = 0.0066), MMSE (P < 0.00001), delayed memory (P < 0.00001), and TMT (P = 0.0021). Age of onset predicted impairment in immediate (P = 0.023) and delayed memory (P = 0.0181), and dyskinesias (P = 0.0006). Although most features of LLD are related to ageing rather than to late-onset, LOD is a possible separate diagnostic entity characterised by memory dysfunction and increased liability to movement disorders.

Automated summary

In late-life depression (LLD), there are differences between patients with late-onset depression (LOD) and early-onset depression (EOD) that may be due to the effects of brain aging. To test this hypothesis, the study analyzed the clinical and cognitive manifestations of 438 outpatients aged >60 years with major depressive disorder. Compared to the EOD group, the LOD group had older patients with lower depression severity, lower global cognitive functioning, and more dyskinesias. Current age and age of onset were found to be correlated with various clinical and cognitive measures. LOD may be a separate diagnostic entity characterized by memory dysfunction and increased liability to movement disorders.