(C-027) Considerations for estimating prevalence and incidence based on systematic literature review: an example in geographic atrophy

Background: Geographic atrophy (GA) is an irreversible, late-stage manifestation of dry age-related macular degeneration. As of 2013, global GA prevalence was estimated at ~0.4%; however, there is no comprehensive, up-to-date assessment of GA epidemiology.

Objectives: To estimate GA prevalence/incidence based on a systematic literature review (SLR) and highlight key considerations for similar analyses.

Methods: A systematic literature search was conducted to identify observational studies on GA prevalence, cumulative incidence, or incidence rate in MEDLINE and Embase from inception to January 22, 2024. Grey literature was also searched, including reference lists of publications identified by the authors and government/non-government reports/databases. Studies based on specific subpopulations (eg, comorbidities, race) or the worse eye only, studies investigating GA combined with other outcomes, and studies reporting the number of eyes rather than individuals were excluded.
Risk of bias was assessed using the JBI Critical Appraisal tool. Data were synthesized with meta-analysis using random effects model with inverse variance, with a Freeman-Tukey double arcsine transformation.

Results: Identified records (780 from MEDLINE and Embase, 134 from grey literature) were screened by 2 reviewers, of which, 162 were selected for full-text review by a single reviewer. 21 studies (20 journal articles and 1 website) met eligibility criteria. Most (17/21 [81%]) had low risk of bias. More than half (12/21 [57%]) were conducted in Europe and most (15/21 [71%]) were published ≥15 years ago. No studies reported race, ethnicity, or genetic details.
Overall, 16 studies reported GA prevalence, with values ranging from 0.20%-6.26%; overall GA prevalence was estimated to be 1.40% (95% CI, 0.78-2.20) by meta-analysis. High interstudy heterogeneity was observed due to divergence in the definition of GA and diagnostic methods. Among the 10 European studies that reported prevalence, GA prevalence was estimated to be 2.07% (95% CI, 1.07-3.36) by meta-analysis.

Conclusions: This SLR indicates that there is limited current literature on GA epidemiology. Identified literature tended to be older and heterogenous. Estimated GA prevalence was higher than previously reported, potentially due to our focus on representative studies only. Newer studies that adopt a standardized definition of GA, use modern diagnostic methods, and report demographics and clinical characteristics in detail are needed to accurately estimate prevalence/incidence and characterize patients to inform future research. Similar considerations may be applicable to other research that aims to estimate disease prevalence and incidence.