Depressive symptomatology has long been shown to be associated with the onset of dementia, though the exact form and directionality of this association remains unclear. While much research has gone into confirming this link, there has been little investigation into the effects of depression on dementia progression after diagnosis. The aim of this study is to investigate the relationship between depressive symptomatology and cognitive and behavioural decline over the following year.

In a Rural and Remote Memory Clinic, 375 patients consecutively diagnosed with mild cognitive impairment (MCI), Alzheimer’s Disease (AD), or non-AD dementia completed the Center for Epidemiological Studies Depression Scale (CES-D) at first visit and one-year follow-up to assess depressive symptomatology. The same cohort were evaluated for cognitive and behavioural decline through the completion of five clinical tests performed at the first visit and at one-year follow-up. Cognitive decline was assessed using the Mini Mental Status Exam (MMSE) and the Clinical Dementia Rating Scale (CDR). Neuropsychiatric symptoms were assessed using two subsets of data from the Neuropsychiatric Inventory (NPI severity and distress), both of which are completed by the patients’ caregivers. Functional decline was assessed using the Functional Activities Questionnaire (FAQ). In both cognitive and functional decline, data were analyzed with linear regression analysis in the population subgroups of All Type Dementia (ATD, which includes MCI for this study) (N=375), Alzheimer’s type dementia (N=187), and Mild Cognitive Impairment (N=74).

In this study, we observed no correlation between CES-D scores at baseline and cognitive or functional decline over one year. However, we observed a significant positive correlation between changes in CES-D scores and NPI-severity scores over one year in patients with ATD (likely the most reliable observation from this study due to larger statistical power) and in the MCI subgroup, but not in the AD subgroup. This relationship may be attributable to a relationship between depression and neuropsychiatric symptoms in general, or to the fact that a person with dementia who exhibits more depressive symptomatology appears more impaired and causes greater distress in their caregivers, despite stability in the objective measures of their cognitive and functional status. This finding may indicate that intervention for depression is needed to alleviated caregiver burden when managing dementia patients.

Increasingly severe depressive symptomatology may exacerbate neuropsychiatric symptomatology but did not correlate with cognitive and functional decline in patients with dementia. More studies are needed to help delineate the relationship between depression and dementia progression.