Background Previous evidence suggests that the presence of affective problems, such as depression and anxiety, may confer an increased risk for late-life dementia. However, the extent to which affective symptoms may influence memory decline in particular, even many years prior to the clinical threshold for a diagnosis of dementia, is not clear. The present study systematically reviews and synthesises the current evidence surrounding the association between depression and memory decline across the life course.
Methods An electronic search of PubMed, PsycInfo and ScienceDirect was conducted to identify studies on the association between depression and subsequent memory decline. Key inclusion criteria were prospective, longitudinal studies with a minimum follow-up period of one year. Cross-sectional, experimental, and clinical (case-control) studies were excluded. Reference lists of relevant papers were scanned for any additional articles of interest. Data extraction and methodological quality assessment using the STROBE checklist were conducted independently by two raters. Multi-level meta-analyses were conducted, with consideration of a number of potential moderators, including mean age of sample at baseline, length of follow-up, and quality of study.
Results After removal of duplicate references, all papers were screened for eligibility using a three-step process: 1) title screening (n=20,954); 2) abstract screening (n=981); and 3) full text screening (n=172). Inter-rater reliability at each stage of screening was >90%. A total of 17 studies (with 8 assessing depression as a binary variable and 9 assessing depression as a continuous variable) met eligibility criteria and had sufficient statistical information for extraction. The results of the meta-analyses will be presented and discussed with a focus on the effects of the key moderators that may influence the link between depression and memory decline, such as mean age at baseline, length of follow-up, and quality of study. Preliminary analyses suggest that affective problems significantly increase risk for subsequent decline in memory (Binary meta-analysis: OR=1.47; 95% CIs=1.15, 1.87, p=0.002; Continuous meta-analysis: B=−0.007, 95% CIs=−0.011,–0.002, p=0.003). Conclusions Results of the present study improve current understanding of the temporal nature of the association between depression and memory across the life-course. This has important implications for the identification of individuals who are at a particularly high risk for accelerated decline in memory function and dementia.
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