ABS0184 SEASONALITY AND LATITUDE: ENVIRONMENTAL DETERMINANTS OF GIANT CELL ARTERITIS INCIDENCE – A SYSTEMATIC REVIEW AND META-ANALYSIS

Abstract

<h2>Abstract</h2><h3>Background:</h3> The incidence of Giant Cell Arteritis (GCA) is influenced by various unexplained factors. It primarily affects Caucasian individuals, with its onset occurring after the age of 50 and peaking at around 70 years old. Women are affected three times more often than men and the incidence increases with latitude in the Northern Hemisphere. Over the past 60 years, studies have investigated seasonal influence on GCA incidence, yielding contradictory results. <h3>Objectives:</h3> This systematic review and metanalysis aims to determine whether there is a pooled seasonal influence on GCA incidence and to explore if this influence is modulated by geographic location and latitude. <h3>Methods:</h3> PubMed and Scopus databases were searched for studies on seasonal influence on GCA incidence without date restriction. Articles reporting incidence and describing seasonal or monthly proportions of GCA as defined by The American College of Rheumatology classification criteria or after positive temporal artery biopsy were considered for inclusion. The primary outcome measured was the Seasonal Incidence Risk Ratio (SIRR) defined as the incidence of GCA in warm seasons (Spring and Summer) over GCA incidence in cold seasons (Autumn and Winter). Meta-analysis of GCA incidence variations with season was performed on the pooled SIRR. <h3>Results:</h3> Nineteen articles describing GCA incidence and seasonal variations in 39,829 patients were included, 10 studies reported a significant seasonal pattern in the incidence of GCA with seven studies reporting a warm seasonal pattern and three studies reporting a cold seasonal pattern while 9 studies did not report a significant seasonal pattern. The pooled SIRR estimate in this metanalysis was 1.08 (95% CI [0.99-1.17]) (Figure 1). We observed a significant reverse correlation between SIRR and the studies' location latitude r=-0.595 (p=0.015). Additionally, we observed an inflexion latitude line in Lyon, France (45.8) (Figure 2), all studies performed southern to that line reported higher proportion of warm seasons cases. The pooled SIRR of studies performed southern to the inflexion line was 1.18 (95% CI [1.09-1.28]). Regarding the meta-analysis of the pooled estimate of SIRR in all included studies, the Egger test (Bias estimate 1.0194; p=0.135) did not support an asymmetrical distribution of the funnel plot, which does not suggest the presence of a publication bias. <h3>Conclusion:</h3> This meta-analysis shows a global pooled trend towards a summer seasonal pattern, mainly driven by southern locations of the included studies, linking two largely discussed environmental factors in GCA which are latitude and seasonal influence which should encourage epidemiological research in southern regions of the world in order to obtain globally representative data. Figure 1Forest plot of the meta-analysis of the pooled seasonal incidence risk ratio.SIRR: Seasonal Incidence Risk Ratio. Figure 2Dichotomous proportion of warm seasons cases displayed in a world map. <h3>REFERENCES:</h3> <b>NIL</b>. <h3>Acknowledgements:</h3> <b>NIL</b>. <h3>Disclosure of Interests:</h3> <b>None declared</b>. © The Authors 2025. This abstract is an open access article published in Annals of Rheumatic Diseases under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Neither EULAR nor the publisher make any representation as to the accuracy of the content. The authors are solely responsible for the content in their abstract including accuracy of the facts, statements, results, conclusion, citing resources etc.