Association between hidradenitis suppurativa and hospitalization for psychiatric disorders: A cross-sectional analysis of the National Inpatient Sample Kevin R. Patel, BS1, Supriya Rastogi, BA1, Vivek Singam, BA1, Harrison H. Lee, BS1, Ahmad Z. Amin, MD1, Jonathan I. Silverberg, MD, PhD, MPH1,2,3 1. Department of Dermatology, Northwestern University Feinberg School of Medicine, Chicago, IL 2. Department of Dermatology, Preventive Medicine and Medical Social Sciences, Northwestern University Feinberg School of Medicine, Chicago, IL 3. Northwestern Medicine Multidisciplinary Eczema Center, Chicago, IL British Journal of Dermatology. DOI: 10.111/bjd.17416

Jonathan I Silverberg, MD, PhD, MPH Kevin R. Patel, MD

Introduction What’s already known? Hidradenitis suppurativa was previously found to be associated with psychosocial distress and some mental health disorders.

Objective To determine whether hidradenitis suppurativa is associated with increased hospitalization for mental health disorders and cost of care.

Methods The 2002–2012 Nationwide Inpatient Sample (NIS) provided by the Healthcare Cost and Utilization Project (HCUP) from the Agency for Healthcare Research and Quality (AHRQ) was analyzed. The databases were searched for a primary and/or secondary diagnosis of hidradenitis suppurativa using the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) code 705.83.

Methods Weighted frequency and prevalence (95% confidence intervals [CI]) of either a primary or any (primary/secondary) diagnosis of a MH disorder was determined among patients with HS and non-HS controls. Survey logistic regression models were used to determine the association of HS and MH disorders.

Methods Survey weighted linear regression was performed with (2) cost of care or (3) length of stay (LOS) as the dependent variables, in order to determine the impact of MH disorders on cost of hospitalization and LOS in HS patients.

Results Overall, 87,053,155 adult and pediatric hospitalizations were captured in the NIS between 2002-2012, with 24,666 admissions with HS (weighted frequency: 116,859). Among inpatients with HS, 490 (2.0%) and 7,904 (32.0%) had a primary or secondary diagnosis of a MH disorder compared with 1,896,921 (2.2%) and 15,349,599 (17.6%) in controls, respectively.

Results In multivariable logistic regression models controlling for age, sex, race/ethnicity, and insurance type, HS was associated with a primary or secondary diagnosis of a MH disorder (aOR [95% CI]: 2.53 [2.42-2.63]). Ten of the 15 MH disorders investigated were associated with HS, including depression, suicidal risk, anxiety, ADD/ADHD or conduct disorder, schizophrenia, personality disorder, substance use disorder, adjustment disorders, developmental disorders, and history of mental health disorder (P<0.0001 for all).

Results In patients with HS, the mean cost of inpatient care for those with vs. without a MH disorder was similar ($10,267 [$9,899-$10,634] vs. $10,082 [$9,728- $10,435], P=0.32). There were an estimated $38,420,492 excess costs of hospital care annually for MH disorders in patients with vs. without HS. The mean LOS was significantly higher in patients with HS (5.89 [5.70-6.07]) vs. without HS (4.75 [4.63-4.87]; P<0.0001) for hospitalization for any MH disorder.

Discussion This study showed a strong relationship between HS and various MH illnesses, including anxiety, schizophrenia, personality disorder, depression, ADD/ADHD, substance use disorder, suicidal risk, adjustment disorders, developmental disorders, and history of mental health disorder. This study confirms and expands upon previous findings that demonstrated increased rates of MH disorders in patients with HS compared to those without the disease.

Discussion HS was linked with increased LOS and cost of hospitalization but was not found to influence inpatient mortality. The results of the present study collectively show that HS is associated with considerably increased morbidity attributed to MH disorders.

Conclusions What does this study add? HS is associated with hospital admission for multiple MH disorders. Future studies are needed to confirm these associations, their underlying relationships, and best approaches for their prevention and treatment.

Researchers Jonathan I Silverberg, MD, PhD, MPH Kevin Patel, MD Supriya Rastogi, MD Harrison Lee, BS Ahmad Amin, MD Vivek Singam, MD

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