The association between vision impairment and depression: a systematic review of population-based studies

Authors: Virgili G, Parravano M, Petri D, Maurutto E, Menchini F, Lanzetta P, Varano M, Mariotti SP, Cherubini A, Lucenteforte E.

Geographical coverage: Europe, United States and Asia.

Sector: Burden of disease

Sub-sector: Epidemiology

Equity focus: None

Study population: General populations

Review type: Other review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis method: Not applicable

Background: Vision loss is associated with reduced performance in activities of daily living, with a greater risk of falls, social isolation, institutionalisation, and even death. Previous reviews demonstrate links between the two conditions; however, there have been no recent reviews or meta-analyses on the burden of the association between VI and depression in the general population.

Objectives: To investigate whether depression is associated with VI in community-dwelling adults.

Main findings

The review confirms that VI and depression are common coexistent morbidities in adults and older people in the general population.

The analysis included 29 studies with participant numbers ranging from 218 to 48,583,771. The studies used survey data (18 studies), clinical examination data (10 studies), and administrative databases (3 studies). They were conducted in Europe (10 studies), the United States (10 studies), Asia (9 studies), and among Cuban American, Mexican American, and Puerto Rican adults (1 study). One study included data from both Europe and North America. Most studies (22) presented raw data with a cross-tabulation of Visual Impairment (VI) and depression. Two studies reported only crude Odds Ratios (OR), three reported only adjusted OR, and four reported both crude and adjusted OR. Most studies had a score of 1 or 2 in the major domains of the quality scale. 14 reached a total score between 8 and 10, while 17 reached a total score between 6 and 7.

The review discovered that the overall proportion of depression was 0.17 (95% CI: 0.13-0.22) and 0.27 (95% CI: 0.21-0.33) in subjects with Visual Impairment (VI). The overall proportion of VI was 0.10 (95% CI: 0.07-0.16) and 0.20 (95% CI: 0.13–0.29) in depressed subjects. The authors reported a direct association between VI and depression, with crude Odds Ratios (ORs) of 1.89 (1.51-2.37) for survey data, 2.17 (1.76-2.67) for clinical examination data, and 3.34 (1.01-11.11) for administrative databases. Adjusted ORs were 1.75 (1.34-2.30), 1.59 (1.22-1.96), and 2.47 (0.97-6.33), respectively. The review confirmed that VI and depression commonly coexist in adults and older individuals in the general population. This association persisted in most studies, regardless of the varying prevalence of either condition or the detection methods used. Surveys reported a higher prevalence of both VI and depression compared to clinical examinations. Subgroup analyses indicated a similar strong association in studies that included younger adults. Authors note that VI and depression are prevalent morbidities and should be actively sought when either is identified, especially in older adults.

Methodology

Studies were included if they provided two-by-two data for calculating the OR of association between VI and depression, or crude and/or an adjusted odds ratio (OR) with a corresponding 95% confidence interval (CI). Authors sought to include population-based cross-sectional studies of community-dwelling adults. Accepted the diagnostic category of VI as applied by the authors of each study, which included the World Health Organization (WHO) definition, US definitions of VI and blindness, self-reported low-vision, registry-based definitions, including administrative/insurance data. For studies using clinical examination, it was planned to use the International Classification of Diseases 11 to create study subgroups according to VI severity, defined according to best-corrected visual acuity (BCVA) in the better eye as mild.

The electronic databases Medline (via PubMed) and EMBASE were searched from inception to 7 June 2020. Four independent reviewers analysed the output of the search and selected the studies, with a duplicate classification of literature and data extraction to ensure accuracy. Discrepancies were solved by an agreement between reviewers or with a senior reviewer.

All included studies were subject to methodological critical appraisal by means of an adapted risk of bias tool for prevalence studies. A maximum of 10 stars was assigned in five domains, with a maximum of two stars for each domain. Pooled study-specific ORs were calculated using the ‘metagen’ command in R software as follows: random-effect models were performed using inverse variance methods for pooling, Der Simonian-Laird estimator for tau2, and the Jackson method for confidence intervals of tau2 and tau. Study-specific proportions were pooled with the ‘metaprop’ command in R software as follows: a random intercept logistic regression model was fitted, used maximum-likelihood estimator for tau2, logit transformation of proportions, and Clopper-Pearson CI for individual studies. Pre-planned heterogeneity investigation was based on age 65 years or more, the inclusion of people with systemic comorbidities, the type of questionnaires used for diagnosing depression, and the definition of VI. Heterogeneity was assessed graphically and by inspecting I² and reporting the predictive interval for primary meta-analyses.

Applicability/external validity: he constraints of the studies included in this review might affect the study’s generalizability. However, the authors illustrate how their results expand on previous reviews.

Geographic focus: The relationship between Visual Impairment (VI) and depression in low and middle-income countries was not specifically examined, even though several studies conducted in these regions were included in the review.

Summary of quality assessment:

While the approaches undertaken to include and critically appraise studies were generally robust, there were weaknesses in the search strategy that may have led to not all relevant studies being included. It appears that the search was restricted to English, and there is no evidence of reference sections of included studies being reviewed, relevant experts contacted or unpublished material being considered for inclusion. The approaches to data analysis were generally robust; however, no attempts were made to explore the impact of including studies with various risks of bias in the final meta-analysis (although the authors do acknowledge the prevalence of various risks of bias among the included studies). For these reasons, we attributed low confidence in the findings of this study.