Obesity and rate of change in body mass index (BMI) as potential risk factors for developing hidradenitis suppurativa (HS) were identified by study data published in the British Journal of Dermatology. By contrast, a diagnosis of HS did not appear to precipitate increases in BMI.

Although prior research has identified an association between obesity and HS, whether obesity is a risk factor for, or a result of, HS remains unknown. To elucidate the direction of this association, investigators conducted a case-control analysis of patients with and without HS using data extracted from the Explorys database. Explorys comprises medical claims data from more than 64 million unique patients from the United States. Adult patients with active status in database from January 1, 1999 to September 9, 2019 were eligible for inclusion. HS was identified using the relevant International Classification of Diseases, Ninth Revision (ICD-9) codes. Eligible patients also had available BMI data from at least 10 consecutive annual visits. Patients with HS were matched 1:1 by age, sex, race, and baseline year to control patients without HS. Linear mixed effects models were used to compare trends in BMI between patients with HS and control patients. BMI was the primary outcome variable in all regression models.

The study cohort comprised 1284 patients with HS and 1284 control patients. Mean age in both groups was 39.2 years. Overall, 84.0% of participants were women, 53.2% were White, and 40.8% were Black. Patients with HS were more likely to report current smoking at baseline compared with control patients (17.5% vs 4.3%). Average baseline BMI was significantly higher among patients with HS compared with control patients (mean difference [MD], 3.03 kg/m2; 95% confidence interval [CI], 2.44-3.62; P <.001). The difference was greater among women (MD, 3.37 kg/m2; 95% CI, 2.73-4.01) compared with men (MD, 1.27 kg/m2; 95% CI, -0.20, 2.73) (P =.01). The case-control difference was also more pronounced in patients diagnosed with HS before age 40 years (MD, 4.10 kg/m2; 95% CI, 3.15-5.06) compared with those diagnosed after age 40 years (MD, 2.38 kg/m2; 95% CI, 1.63-3.12) (P <.001). Before diagnosis, mean annual change in BMI was slightly higher among patients with HS compared with control patients. However, after diagnosis, annual changes in BMI were comparable in the groups.

Per these data, obesity appears to be a risk factor for HS, the investigators believe. Diagnosis of HS did not appear to influence rate of BMI growth, suggesting that high BMI may not be a direct consequence of HS. Differences between patients with HS and control patients were most pronounced among women and younger patients.

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Study limitations include the lack of data on certain covariates, such as socioeconomic status. Further study is necessary to better understand the relationship between HS and weight, among other potential risk factors.

“In conclusion, baseline BMI and, to a lesser extent, rate of BMI change appear to be risk factors for developing HS,” investigators wrote. “[However]… findings in this study should not further stigmatize patients who are afflicted with HS…[I]t is essential that clinicians do not ascribe development of HS to obesity alone.”

Disclosure: This study was supported in part by an education grant from AbbVie. Several study authors declared affiliations with the pharmaceutical industry. Please see original reference for a full list of authors’ disclosures.


Wright S, Strunk A, Garg A. Trends in body mass index before and after diagnosis of hidradenitis suppurativa [published online December 10, 2020]. Br J Dermatol. doi: 10.1111/bjd.19713