OBJECTIVE: To investigate whether depression is independently associated with increased risk of incident dementia or cognitive disorder not otherwise specified (NOS) in an older primary care population. METHOD: This was a prospective 3-year cohort study of 470 patients aged >or= 65 years without baseline cognitive disorders who were recruited from primary care offices. Annual assessments completed from March 2003 through December 2005 included the use of the Structured Clinical Interview for DSM-IV to diagnose major depressive disorder (MDD) and minor depression (MinD) and the Hamilton Depression Rating Scale (HDRS) for depressive symptom severity. The Mini-Mental State Exam, Mattis Dementia Rating Scale-initiation/perseveration subscale, and the Trail Making Tests A and B informed diagnoses of dementia and cognitive disorder NOS. RESULTS: 36 subjects, representing a cumulative incidence of 13%, developed dementia or cognitive disorder NOS over 3 years. Using Cox proportional hazard survival models to calculate the risk ratio of depression for development of cognitive disorders, MDD and MinD (HR = 3.68; 95% CI, 2.1-6.42 and HR = 1.84; 95% CI, 1.05-3.21, respectively) and HDRS scores (HR = 1.07; 95% CI, 1.02-1.12) predicted new onset dementia or cognitive disorder NOS, when covarying age, gender, and education. CONCLUSIONS: Depressive disorders pose increased risk of incident dementia or cognitive disorder NOS in older primary care patients. Clinicians treating depressed older adults should monitor for development of cognitive disorders.
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