Longitudinal study of chronic depressive symptoms and regional cerebral blood flow in older men and women

Abstract

Late-life depression is associated with alterations in regional cerebral blood flow (rCBF) and metabolism in a neural network that includes frontostriatal and limbic regions and the cerebellum. Prior studies suggest that clinical depression and subthreshold depressive symptoms (SDS) are associated with similar cognitive deficits and structural brain changes, but little is known about the relationship between SDS and patterns of brain activity. Additionally, the neural correlates of depression have not been fully explored in men and women separately. This study investigated cross-sectional and longitudinal relationships between SDS and rCBF in older men and women. Sixty-one dementia-free older adults (35 men, 26 women), 56 years of age and older at baseline, from the neuroimaging substudy of the Baltimore Longitudinal Study of Aging participated. Participants underwent resting-state PET scans at baseline and at year 9 and completed the Center for Epidemiologic Studies Depression Scale annually. At 8-year follow-up, both men and women showed cross-sectional associations between mean depressive symptom scores and activity in primarily frontal and temporal regions and the cerebellum. Higher average depressive symptoms were associated with longitudinal rCBF decreases in frontal regions in both men and women, and in temporal regions in men. Regions showing associations between activity and SDS were similar to those found in studies of clinical depression, providing support for the hypothesis that depressive syndromes exist on a continuum of severity. Sex differences in associations provide some evidence that the pathophysiology of depressive disorders differs between men and women.