Hidradenitis Suppurativa in Sweden: A Registry-Based Cross-Sectional Study of 13,538 Patients

Background: Hidradenitis suppurativa (HS) is a chronic, inflammatory skin condition with nodules and fistula formation and scarring. It is a debilitating disease with a severe negative impact on quality of life. There is a need for increased knowledge about the social and lifestyle characteristics of patients with HS in general, and pregnant women in particular. Objectives: The aims of this study were to investigate and describe social characteristics and comorbidity in all HS patients in Sweden as well as to study the prevalence of lifestyle factors associated with negative impact on health and pregnancy in Swedish pregnant women with HS. Methods: A registry-based cross-sectional study was performed by record linkage between Swedish registers covering the entire population. A cohort of 13,538 HS patients diagnosed with HS in specialised care during the years 2001-2014 and a subgroup of 1,368 HS patients who had undergone pregnancy during 2010-2015 were defined and described. Aggregated public data on the entire Swedish population and all pregnancies in 2014 were described for reference. Results: The HS population had an average age of 44 years on December 31, 2014. The prevalence of HS was 0.14%. In comparison to the Swedish reference population the HS patients were more often women, unmarried (36 vs. 44% married), and had lower education (68 vs. 82% with an upper-secondary school degree or higher) and lower income (39 vs. 16% made SEK <100,000 a year). Comorbidity was 3% for inflammatory bowel disease and 8% for type 2 diabetes. The subgroup analysis showed high prevalence of overweight, obesity, and smoking in pregnant women with HS. Conclusions: The results from this comprehensive characterisation of Swedish HS patients may be used to improve preventive measures, information, and care for this vulnerable group.