Longitudinal follow-up of depressive symptoms among normal versus cognitively impaired elderly

This prospectively designed longitudinal study assesses prevalence, incidence and prognosis of depressive symptoms among cognitively normal elderly volunteers compared with patients with mild cognitive impairment (MCI), dementia of Alzheimer type (DAT), and vascular dementia (VAD). Possible relationships between depressive symptoms, cognitive performance, disease types, and effects of antidepressant treatment were analyzed.

Two hundred and ninety four subjects exhibiting different levels of cognitive performance were admitted to this study. Demographics, cardiovascular and neurodegenerative risk factors, together with measures of neuropsychological test performance, were obtained at sequential visits. Depressive symptoms were selectively treated with antidepressant medications.

One hundred and forty six subjects with normal cognition, 19 subjects with MCI, 42 patients with DAT, and 32 patients with VAD were followed for a mean of 3.5 years. With the passage of time, there were trends showing prevalence of depressive symptoms to decrease among DAT and to increase among VAD patients. VAD patients exhibited the highest incidences of new-onset depressive symptoms, followed in incidence by DAT and MCI groups. Depressive symptoms among VAD and MCI patients were more persistent and refractory to antidepressant medications than for DAT patients. Trends suggested that antidepressant treatment might benefit MCI and VAD subjects more than DAT patients. Motivationally related depressive symptoms accounted for major components of elevated Hamilton depression rating scale scores.

Depressive symptoms among DAT patients have higher rates of spontaneous resolution, without requiring intensive drug treatment, than among VAD patients in whom depressive symptoms are more persistent and refractory to drug treatment. Early depressive symptoms among subjects with MCI may represent a preclinical sign and should be considered as a risk factor for impending DAT or VAD among the elderly.