Prevalence of Cognitive Impairment among major depressive disorder patients: A systematic review and meta-analysis

INTRODUCTION Cognitive impairment is a common but undetected symptom among Major Depressive Disorder patients that can impact daily functioning and quality of life. There has not been comprehensive study assessing cognitive impairment among major depression patients despite the considerable risk of exposure. Therefore, this review was designed to assess global pooled prevalence of cognitive impairment among major depression patients. METHOD This systematic review was done according to PRISMA guidelines, with searches in electronic databases such as Google Scholar, PubMed, and Scopus. The quality of the studies included was determined by the JBI Quality Assessment Scale. Extraction of the data was performed with Microsoft Excel, and meta-analysis was done using STATA 17 software. The random-effects model was used to synthesize the pooled prevalence cognitive impairment in major depressive disorder. Besides, heterogeneity was explored using meta-regression and subgroup analysis. Publication bias was evaluated using funnel plots and Egger's statistical tests. Sensitivity analysis was also performed. RESULTS The pooled overall prevalence of cognitive impairment in patients with major depressive disorder (MDD) was 53% (95% CI: 41% – 64%). Heterogeneity between the studies was very high (I² = 98.76%). Subgroup analyses were conducted to examine the potential sources of heterogeneity. Study design was one of them. The subgroup pooled estimates are by Cross-sectional: 58.3%, Cohort: 42.5% and Case-control: 26.6%. Based on cognitive assessment tools suggested the highest overall proportion was observed in studies using the MMSE 66.9% and the lowest pooled prevalence was observed using the DASST tool 35.5%. The highest pooled prevalence was between studies that used the ICD-10 criteria to diagnose MDD, with rate of 70.4%, followed by clinical diagnosis 63.6%, DSM-V 58.1%, DSM-IV 40.4% and the MINI 7.0 study had the least estimate 32.7%. Publication bias was assessed using Begg's and Egger's tests, neither of which indicated bias at a significant level (p > 0.05). The trim-and-fill method confirmed the stability of the findings, with no imputed absent studies. Sensitivity analysis demonstrated that the overall effect size remained stable in all iterations. CONCLUSIONS This meta-analysis found the pooled prevalence of cognitive impairment in major depressive disorder (MDD) was relatively high across the included studies However, there was notable variability was observed based on diagnostic criteria, study design, and cognitive measurement instruments. Although the findings suggest the potential value of including routine cognitive screening and cognitive symptoms in treatment protocols, the limited number of studies (n = 11) warrants cautious interpretation. Future research using consistent diagnostic and cognitive assessment methods is recommended to confirm these findings and guide clinical practice.