Absence of effect of depression on cognitive performance in early-stage Alzheimer disease.

ABSTRACT

BACKGROUND: Depression can interfere with the normal expression of cognitive abilities in adults of all ages, but it is unclear if depression in demented people, which is common, is associated with reduced cognitive performance beyond the effect of the dementia itself. OBJECTIVE: To determine if depression adds to the cognitive deficit in dementia. DESIGN: Performance on psychometric tests of memory and other cognitive function was correlated with the number of depressive features reported by the individual and by a knowledgeable collateral source, as well as the judgment of a research clinician as to whether the person was depressed. SETTING: An Alzheimer disease research center. PARTICIPANTS: The convenience sample included individuals with very mild (Clinical Dementia Rating, 0.5; n = 167 [mean age, 76.03 years]) or mild (Clinical Dementia Rating, 1; n = 155 [mean age, 78.41 years]) Alzheimer disease who were enrolled in ongoing longitudinal studies at the center. MAIN OUTCOME MEASURES: Psychometric measures of memory and cognition. RESULTS: Depression was present in 15% of the very mild and 24% of the mild dementia groups. There was no relation between the clinicians' diagnoses of depression and psychometric scores. Little relation was found between performance on the cognitive tests and the number of depressive features (maximum, 9) reported by the individual or collateral source. The few statistically significant (P<.05) correlations were modest (< or =0.21). CONCLUSION: Depression does not worsen cognitive test performance beyond the effect of dementia.