Smoking as a risk factor for giant cell arteritis: A systematic review and meta-analysis

To investigate the association between smoking and giant cell arteritis (GCA). A systematic review was performed and meta-analysis conducted on observational studies that reported absolute numbers and/or statistical comparisons with 95% confidence intervals comparing smoking history and presence of GCA, among patients with GCA and non-GCA controls. Studies were reviewed in accordance with PRISMA guidelines. Point estimates and standard errors were extracted from individual studies and were combined by the generic inverse variance method of DerSimonian and Laird. A random-effects meta-analysis was performed. Statistical heterogeneity was assessed using the Cochran's Q test which was complemented with the I2 statistic. The initial search yielded 3312 articles. Of these, thirteen studies (8 prospective and, 5 retrospective case-control studies) with unique cohorts were identified and included in the primary analysis (ever vs. never smoking history). Patients in the GCA cohort were more likely to have a history of smoking with an odds ratio of 1.19 (95% CI, 1.01–1.39). Considerable heterogeneity was present (I2 = 85%). Five of these studies included information on current smoking status. One additional study, which only reported current smoking status, was also included. The GCA cohort showed an association with current smoking with an odds ratio of 1.18 (95% CI, 1.01–1.38). Our study demonstrated a statistically significant increased risk of GCA among both current and ever smokers compared to non-smokers.