Background: We assessed the relationship between cognitive impairment (including mild cognitive impairment with no signs of dementia, and dementia) and risk for depression in old age (60 years and older).
Methods: MEDLINE, EMBASE and the Cochrane Library database were used to identify potential studies. All of the clinical studies that produced data on the association between cognitive function and risk of depression among individuals aged 55 years or older were identified and included in this review. The studies were classified into cross-sectional and longitudinal subsets. The quantitative meta-analysis of cross-sectional and longitudinal studies were performed. For prevalence and incidence rates of depression, odds risk (OR) and relative risk (RR) were calculated, respectively.
Results: Since all but two studies found in the search were for individuals aged 60 years or over, we assessed and reported on results for this larger group only. In this review we included 13 cross-sectional and four prospective longitudinal studies. The quantitative meta-analysis showed that, in old age, individuals with non-dementia cognitive impairment had neither significant higher prevalence nor incidence rates of depression than those without (odds risk (OR): 1.48, 95% confidence intervals (95% CI): 0.87-2.52; relative risk (RR): 1.12, 95% CI: 0.62-2.01). In old age, individuals with dementia had both significant higher prevalence and incidence rates of depression than those without (OR: 1.82, 95% CI: 1.15-2.89; RR: 3.92, 95% CI: 1.93-7.99).
Conclusions: Despite the methodological limitations of this meta-analysis, we found that in old age, there was no association between depression and cognitive impairment with no dementia; however, there was a definite association between depression and dementia and thus dementia might be a risk for depression.