Prevalent depressive symptoms as a risk factor for conversion to mild cognitive impairment in an elderly Italian cohort

Objective: To examine the association between depressive symptoms and prevalent and incident mild cognitive impairment (MCI) in elderly individuals; to verify whether it is affected by MCI subtype. Design: Prospective, population-based, longitudinal cohort study. Setting: Adults >= 65 years resident in an Italian municipality. Participants: Baseline data are for 595 subjects with no cognitive impairment (NCI) and 72 subjects with prevalent MCI. NCI subjects underwent a 4-year follow-up for incident MCI. Measurements: MCI was diagnosed according to international criteria and classified as with (m + MCI) or without memory impairment (m - MCI). Baseline depressive symptoms were measured using the 30-item Geriatric Depression Scale (GDS). Baseline use of antidepressants was also recorded. Results: Baseline depressive symptoms (GDS >= 10) were more frequent in prevalent MCI cases (44.4%) than in NCI participants (18.3%). The association was independent of MCI subtype, antidepressant use, and sociodemographic and vascular risk factors. In NCI subjects, baseline depressive symptoms were also associated with increased risk of MCI at follow-up, but only for subjects on antidepressant drugs at baseline (incident cases = 72.7%) compared with those without depressive symptoms and not on antidepressant therapy (incident cases = 24.0%). The association was independent of other confounders and stronger for m - MCI (incident cases = 45.4%) with respect to m + MCI (incident cases = 27.3%). Conclusions: Depressive symptoms are highly prevalent among elderly MCI subjects and, in cognitively normal elderly individuals, are associated with an increased risk of developing MCI. The association is stronger for the MCI subtype without memory impairment.