Obesity is not associated with severe chronic urticaria in a French cohort

Editor We recently read with interest the article by Shalom et al., which reported in multivariate analysis, an association between chronic urticaria (CU) and metabolic syndrome (MS) in a crosssectional community-based study of 11 261 patients with chronic urticaria (CU) compared to control (odd ratio: 1.12 95% CI: 1.05–1.21, P = 0.001). With this regard, we would like to make several comments. Recently, another European Italian observational study reported a significant relationship between obesity and chronic spontaneous urticaria (CSU) compared with controls (odds ratio: 1.53 95% CI: 1.08–2.17), from a computer-based survey in 3489 patients with CSU. The major bias of these cross-sectional studies is the temporal relationship between the diagnoses of metabolic syndrome (MS) and obesity, and CU. A recent review has reported preliminary evidence from the limited data currently available which support the association between CU and MS. We report here a French national, non-interventional, multicentre study, which included 278 patients with CU, CSU and CIU, recruited from outpatient consultations, by physician members of the Urticaria Group of the French Society of Dermatology, over a period of 10 months (2015–2016) in 16 university hospitals. In this study, 202 (73%) were obese; 139 (50%) had an abdominal obesity; and 63 (23%) had both abdominal and general obesity (obesity and abdominal obesity were respectively defined with body mass index: BMI ≥30 kg/m and waist circumference ≥80 cm for females and 94 cm for males). In the obese group, the mean BMI and the mean waist circumference were, respectively, 28.6 5.8 and 99.5 12.9 cm compared with 21.7 2.7 and 76.4 9.6 cm in the non-obese group (Table 1). Among the factors that can promote obesity, regular physic activity was documented in 37% of the obese patients, which was significantly lower than physical activity reported in the non-obese group (46%). Similarly, the use of antidepressant treatments was significantly more frequent in the obese group compared with the nonobese group (7.5% vs. 4%, respectively). Severity of CU (defined with urticaria control test (UCT) ≤5/16 and/or the dermatology life quality index (DLQI) ≥11/30) was similar in both obese and non-obese patients; UCT and DLQI scores were 7.8 4.8 and 8.4 6.99, respectively, in the obese group vs. 7.5 4.7 and 8.6 7.1 in the non-obese group. Using multivariate analysis, obesity was not associated with severe CU after adjustment for confounders (in addition to obesity, a model adjusted on age, sex, chronic used of corticosteroids and antihistamine treatment was used) (OR = 1.42 [95% CI: 0.81–2.52]). In terms of systemic steroids use for CU, short courses of corticosteroids were more frequently found in the non-obese than the obese group (60.5% vs. 44%, respectively) while continued corticosteroids were more frequent in the obese than in the non-obese group (12% vs. 5%, respectively). Forty-seven per cent and 46% of the patients in the non-obese and obese groups respectively used at least four daily tablets of antihistamines. Using multivariate analysis, chronic use of antihistamines (OR: 0.99; 95% CI 0.97–1.03, P = 0.92) or corticosteroids (OR: 1.01; 95% CI 0.99–1.02, P = 0.29) was not associated with CU severity or with obesity. The present data from a nationwide survey indicate that the characteristics of patients with CU differ according to BMI; obesity, however, was not associated with severe CU in our cohort after adjustment. Our study suffers the same limitations as all observational studies: namely, no causality can be asserted between parameters that are correlated. Larger prospective studies investigating the link between the metabolic syndrome and the severity of CU seem important to achieve optimal management of patients.