Double trouble: Long COVID-19 and the onset of type 2 diabetes mellitus - a systematic review

Objective: This systematic review aims to clarify COVID-19's impact on the onset of T2D in adults. Material and methods: Following PRISMA guidelines, this systematic review sourced data from multiple databases from 2019 to April 20th, 2023. Two reviewers handled screening, with a third-party resolving disagreement. The focus was on COVID-19 cases with post-infection T2D symptoms persisting for two or more months. Exclusions included those outside the 18-70 age range, prior T2D history, pregnancy, and animal studies. Rayyan software facilitated article screening, STATA 18 performed meta-analysis, and bias was assessed using JBI tools. The study is registered in PROSPERO (ID: CRD42023414096). Results: A total of 173 articles were retrieved, of which 23 (11.6%) remained for extraction. 13 cohort studies with 11.551.026 participants were included for the meta-analysis, which found that the COVID-19 population had 1.4 greater risk of being diagnosed with T2D in comparison with the population without COVID-19or with other respiratory diseases. The other study designs were narratively analyzed, describing similar results as the meta-analysis. Discussion: New onset T2D is a potential consequence of LC. While T2D increases COVID-19 complications, the relationship appears bidirectional. Given the novelty of the topic and potential newer studies, further reviews are needed to understand LC's impact on chronic diseases like T2D globally. Further studies should be carried out on this specific topic that could raise the burden of T2D between all the other symptoms that may be caused by LC. In addition, it is necessary to adapt the interventions according to each country's possibilities.