Effects of temperature, weather, seasons, atmosphere, and climate on the exacerbation of inflammatory bowel diseases: A systematic review and meta-analysis

Background: Exacerbation of inflammatory bowel disease (IBD) is common. Identification of the exacerbating factors could facilitate interventions for forecastable environmental factors through adjustment of the patient’s daily routine. We assessed the effect of natural environmental factors on the exacerbation of IBD. Methods: In this systematic review and meta-analysis, studies published from January 1, 1992 to November 3th, 2022 were searched in the MEDLINE, Embase, CINAHL Complete and Cochrane Library databases. We extracted data related to the impact of environmental variations on IBD exacerbation, and performed a meta-analysis of the individual studies’ correlation coefficient χ2 converted into Cramér’s V (φc) with 95% confidence intervals (CI). Results: A total of 7,346 publications were searched, and 20 studies (sample size 248–84,000 cases) were selected. A meta-analysis with seven studies was performed, and the pooled estimate of the correlation (φc) between the seasonal variations and IBD exacerbations among 4806 cases of IBD exacerbation was 0.11 (95% CI 0.07–0.14; I2 = 39%; p = 0.13). When divided into subtypes of IBD, the pooled estimate of φc in ulcerative colitis (six studies, n = 2649) was 0.07 (95% CI 0.03–0.11; I2 = 3%; p = 0.40) and in Crohn’s disease (three studies, n = 1597) was 0.12 (95% CI 0.07–0.18; I2 = 18%; p = 0.30). Conclusion: There was a significant correlation between IBD exacerbation and seasonal variations, however, it was difficult to synthesize pooled results of other environmental indicators due to the small number of studies and the various types of reported outcome measures. For clinical implications, additional evidence through well-designed follow-up studies is needed. Protocol registration number (PROSPERO): CRD42022304916.