Incidence and remission rates of self-reported hidradenitis suppurativa - A prospective cohort study conducted in Danish blood donors

BACKGROUND: A large discrepancy between physician-diagnosed and self-reported HS exists. Knowledge regarding incidence and remission rates of self-reported HS is missing, but may help bridge the gap in understanding between these two phenotypes.

OBJECTIVES: To determine the incidence and remission rates of self-reported HS, and to what degree these are affected by sex, smoking and BMI.

METHODS: A prospective cohort of 23,930 Danish blood donors. Information on self-reported HS, symptom-localization, sex, age, BMI and smoking status was collected at baseline and study termination. Self-reported HS fulfilled clinical obligatory diagnostic criteria. Cox proportional hazards regression analyses were conducted for both incidence and remission rates providing a hazard ratio (HR) of risk for each variable in the regression.

RESULTS: incidence rate of self-reported HS was 10.8/1,000 person-years (95% CI: 9.9-11.7), decreasing as a function of numbers of areas affected. Female BMI points above 25 (HR=1.11, 95% CI: 1.09-1.13), male BMI points above 25 (HR=1.07, 95% CI: 1.04-1.11) , active smoking (HR=1.72, 95% CI: 1.15-2.57), male sex (HR=0.55, 95% CI: 0.45-0.67) and years of age above 25 (HR=0.97, 95% CI: 0.96-0.97) were all statistically associated with the development of self-reported HS. Remission rate of self-reported HS was 256.7/1,000 person-years (95% CI: 223.9-292.6), decreasing as a function of numbers of affected areas. Symptoms in ≥3 areas (HR=0.54, 95% CI: 0.34-0.85), active smoking (HR=0.49, 95% CI: 0.32-0.76) and female weight loss (every percentage drop in BMI: HR=1.07, 95%CI: 1.05-1.11) all significantly affected the remission rate.

CONCLUSIONS: Both incidence and remission rates of self-reported HS are high, indicating that many with self-reported HS are unlikely to be diagnosed, as they to a higher degree experience mild transient HS symptoms.