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Meta-Analysis
. 2021;8(3):277-285.
doi: 10.14283/jpad.2021.27.

Association of Subjective Cognitive Decline with Risk of Cognitive Impairment and Dementia: A Systematic Review and Meta-Analysis of Prospective Longitudinal Studies

X-T Wang  1 , Z-T Wang, H-Y Hu, Y Qu, M Wang, X-N Shen, W Xu, Q Dong, L Tan, J-T Yu
Affiliations
Meta-Analysis

Association of Subjective Cognitive Decline with Risk of Cognitive Impairment and Dementia: A Systematic Review and Meta-Analysis of Prospective Longitudinal Studies

X-T Wang et al. J Prev Alzheimers Dis. 2021.

Abstract

Background: Subjective cognitive decline (SCD) as an early pathological manifestation of brain aging has become more prevalent among older adults.

Objectives: We aimed to investigate the associations of subjective cognitive decline (SCD) with the combined risk of cognitive impairment and dementia.

Design: We performed a systematic review and meta-analysis via searching Embase, PubMed and Cochrane electronic databases from January 1 st 1970 to June 4th, 2020.

Setting: Prospective cohort studies Participants: Healthy individuals were recruited from community, clinics and population.

Measurements: Healthy individuals with SCD were classified into exposure groups, while those without were considered as the reference group. Adjusted relative risks (RR) were estimated in a random-effects model. Both primary and subgroup analyses were conducted.

Results: Of 28,895 identified studies, 21 studies containing 22 cohorts were eligible for inclusion in the meta-analysis. SCD increased the risk of subsequent cognitive disorders (RR=2.12, 95% confidence intervals [CI] =1.75-2.58, I2=87%, P<0.01). To be specific, SCD conferred a 2.29-fold excess risk for cognitive impairment (RR=2.29, 95% CI=1.66-3.17, I2=83%, P<0.01) and a 2.16-fold excess risk for dementia (RR=2.16, 95% CI=1.63-2.86, I2=81%, P<0.01). In subgroup analyses, participants with SCD in the subgroup of 65-75 years old, long-education (>15 years) subgroup and subgroup of clinics showed a higher risk of developing objective cognitive disorders.

Conclusions: SCD is associated with an increased combined risk of cognitive impairment and incident dementia and should be considered a risk factor for objective cognitive disorders.

Keywords: Subjective cognitive decline; cognitive impairment; dementia; meta-analysis; systematic review.

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Conflict of interest statement

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Figures

Figure 1
Figure 1
The flowchart of study selection *: A study contains two cohorts, &: two studies with specific data on both cognitive impairment and dementia; #: Only three of five studies with specific data of both Alzheimer's disease and non-Alzheimer's disease.
Figure 2
Figure 2
SCD shows a significant association with the risk of developing objective cognitive disorders RR: relative risk, CI: confidence interval, SCD: subjective cognitive decline.
Figure 3
Figure 3
SCD shows significant associations with cognitive impairment and dementia RR: relative risk, CI: confidence interval, SCD: subjective cognitive decline
See this image and copyright information in PMC

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