Mendelian randomization studies in ankylosing spondylitis: A systematic review

Previous research has revealed connections between ankylosing spondylitis (AS) and comorbid conditions. However, observational studies frequently encounter difficulties in establishing definitive causal links between potential risk factors and AS. In contrast, Mendelian randomization (MR) offers a more robust approach to exploring causality by leveraging the random allocation of alleles at birth, thereby minimizing confounding factors.

The PubMed, Web of Science, and Cochrane databases were searched for MR studies related to AS with a time frame of database creation to May 2024. Information on authors, exposures, outcomes, data sources, SNPs, MR analysis methods, ORs (95% CIs), and p-values was extracted. Quality assessment was performed using the Critical Appraisal Skills Program (CASP) checklist.

We systematically reviewed 42 MR studies in AS. Health behaviors, comorbidities, and serum markers were involved. Overall, physical activity, inflammatory bowel disease, and specific intestinal flora with serum markers as exposures were causally associated with AS, which leads to an increased risk with several comorbidities.

MR is a powerful tool for assessing causal relationships between risk factors and outcomes. Specific intestinal flora and inflammatory bowel disease appear to be uncontroversial risk factors that increase the risk of AS. Reliable and robust MR findings may provide a more comprehensive health management strategy for patients with AS.