Effectiveness of N-3 fatty acids supplementation on spondyloarthritis: A systematic review and meta-analysis

The study aims to systematically review and meta-analyze randomized controlled trials (RCTs) assessing the effects of n-3 fatty acids (FA) supplementation on spondyloarthritis (SpA) disease activity, inflammatory markers, and imaging.

The study protocol was developed and registered online in advance. The PubMed, SCOPUS, and Cochrane Central Register of Controlled Trials (CENTRAL) electronic databases were systematically searched for RCTs up to April 2024. Two independent reviewers screened, assessed for eligibility, and extracted data from the eligible RCTs. The revised Cochrane Risk of Bias tool was used to assess the quality of trials. The random-effects model was used to calculate the pooled estimates.

We included four RCTs, involving 245 patients with SpA. Supplementation with n-3 FA did not improve physician-reported outcomes [number of tender joints (four trials, standardized mean difference (SMD): -0.22; 95 % confidence interval (CI): -0.74 to 0.29; I² = 61 %), number of swollen joints (two trials, SMD: -0.13; 95 % CI: -0.42 to 0.15; I² = 0 %)], and patient-reported outcomes [pain (three trials, SMD: -0.16; 95 % CI: -1.03 to 0.70; I² = 74 %), Health Assessment Questionnaire (three trials, SMD: -0.04; 95 % CI: -0.78 to 0.70; I² = 71 %). The other nine pre-specified outcomes were not analyzed due to lack of information from the original RCTs which were evaluated as «some concerns» or «high risk» of bias.

In the present systematic review and meta-analysis including placebo-controlled RCTs, n-3 FA supplementation did not show improvement in the reported outcomes. Future RCTs should be conducted with homogenous intervention, placebo, and outcomes to re-examine possible beneficial effects.