Association of obesity with inflammatory skin disease: An inpatient population study

Obesity as a risk factor has been predominately associated with psoriasis and hidradenitis suppurativa in cutaneous pathology, but limited studies have explored the connection to other diseases within the inflammatory skin domain.1 We investigated the relationship between obesity and common inflammatory skin diseases among adult inpatients in the United States utilizing discharge data from the National Inpatient Sample (NIS) provided by the Healthcare Cost and Utilization Project (HCUP). Male and female adults ≥18 years admitted from 2016 to 2019 were included. We used ICD10-CM codes to define exposure and outcome disease conditions. The exposure variables were the primary and secondary diagnoses of obesity and morbid obesity. Outcome variables were primary and secondary diagnoses of the 24 most common inflammatory skin diseases. The sample was summarized with unweighted and survey-weighted frequencies, survey-weighted prevalence, 95% confidence intervals (CI) and multivariable logistic regression adjusting for covariables to report odds ratio (OR). Covariates included age, sex, race and medical comorbidities. Both obese and non-obese inpatients were analysed. Table 1 provides prevalence data between these groups, as well as odds ratios, unweighted absolute numbers, weighted frequencies and prevalence rates for each inflammatory skin disease among obese and morbidly obese groups. Increased BMI has been reported to cause alterations in skin physiology and immune-mediated changes that can contribute to the development of inflammatory skin states through dysfunctional cutaneous layers.2, 3 Our study found that one of the highest associations between obesity and inflammatory skin disease was with the diagnosis of rosacea (OR = 2.26; 95% CI 2.17–2.34). Prior studies have reported an increased risk of rosacea in cohorts of US women with high BMIs.4 This association may be due to rosacea having similar pathogenic pathways and associations with diseases featuring chronic inflammation and central obesity, such as metabolic syndrome.5 While it is unclear why rosacea had lower odds ratio in the morbid obesity group (OR = 1.52; 95% CI 1.45–1.59), it could be that in morbid patients there are certain comorbidities either less reported or better treated. When examining morbid obesity, our study found the greatest associations with plaque psoriasis (OR = 5.05; 95% CI 4.77–5.34), lichen simplex chronicus (OR = 3.69; 95% CI 3.44–3.96) and pyoderma gangrenosum (OR = 3.14; 95% CI 2.95–3.34). One possible hypothesis for the dose–response relationship with degree of obesity could be increased IL-6, IL-17 and TNF-a activity. 6, 7 The correlation between morbid obesity and lichen simplex chronicus elevations might be difficult to assess with this study as it shares a disease code with neurodermatitis; a disease state where excoriations are associated with components of stress and anxiety and begs the question of whether it is the physical state of morbid obesity elevating the association or the stressors that come for patients living with morbid obesity. This cross-sectional study is limited by its inability to establish causality. Potential confounding factors and the lack of longitudinal data further constrain the interpretation of the result. Future studies should focus on longitudinal data to establish temporal relationships and investigate the underlying biological mechanisms linking obesity to inflammatory skin disease. Our findings are also limited to hospitalized inpatients, who may differ from the general population in disease burden and healthcare access. As such, caution should be exercised when generalizing these findings. Further details on the statistical associations are presented in Table 1. This includes both unweighted absolute numbers, weighted frequencies and prevalence rates for each inflammatory skin disease among obese, morbidly obese and non-obese groups. None. None. Conflicts of Interest: Siri Choragudi, Luis F. Andrade, Omar Mahmoud and Scott A. Elman have no relevant financial or non-financial interests to disclose and no competing interests to declare. Dr. Gil Yosipovitch serves as an advisory board member for Abbvie, Arcutis, BMS, Cara Therapuetics, GSK. Escient Health, Eli Lilly, Galderma, Kiniksa Pharmaceuticals, LEO Pharma, Novartis, Pfizer, Pierre Fabre, Regeneron Pharmaceuticals, Inc., Sanofi, TreviTherapeutics and Vifor. Dr. Gil Yosipovitch receives grants/research funding from Eli Lilly, Kiniksa Pharmaceuticals, LEO Pharma, Novartis, Pfizer, Galderma, Escient, Sanofi Regeneron and Celldex. Dr. Gil Yosipovitch is an investigator for Regeneron Pharmaceuticals, Inc. and Sanofi. Exempt. Not applicable. The data underlying this article will be shared on reasonable request to the corresponding author.