HS tarda: defining an understudied population of hidradenitis suppurativa among elderly

Background: Hidradenitis suppurativa (HS) is a chronic, devastating multifactorial skin disease. Patients generally develop HS after puberty and the prevalence of the disease is assumed to decrease with higher age. Data outside the known age range is limited, although elderly HS patients are seen occasionally at the outpatient clinic.
Objective: To investigate the prevalence, clinical characteristics, and associated comorbidities among the elderly HS population.
Methods: Data was collected through a population-wide survey-based study within the Lifelines Cohort Study, conducted in the Northern Netherlands. The clinical characteristics of elderly HS patients (>60y) were compared to a common adult HS (<60y) population. The associated comorbidities in elderly HS patients were compared to a non-HS sex- and age-matched elderly population in a 1:4 ratio. HS in elderly was defined as active HS in patients aged 60 years and older. Two subgroups were made, respectively, late-onset HS (HS developed after 60 years of age) and persistent HS (HS developed at younger age but continued after 60 years of age). 
Results: The Lifelines cohort consisted of elderly patients with active HS (N=209), an adult (<60y) HS group (N=793) and a non-HS sex- and age-matched control group (N=810) . A total prevalence of 1.0% [95% CI 0.9 to 1.2] of HS in elderly was found among the elderly population. A significantly higher age of symptom onset was found in the elderly HS group, compared to the adult HS group (respectively, 40.0 years vs. 23.0 years [OR=1.056;95%CI 1.05-1.07]). The female-to-male ratio was 1.7:1.0 in the elderly HS group. Moreover, the elderly HS patients had a significantly higher risk of having acne, psoriasis, diabetes, asthma, irritable bowel syndrome, fibromyalgia and PCOS.
Conclusions: This study reveals a higher prevalence of HS in elderly than previously presumed. The elderly HS patients displayed significant variations in the disease course, such as age at symptom onset and involved body areas. Moreover, the elderly HS patients were more susceptible to multimorbidity than age-matched controls, which indicates a higher risk for frailty. In addition, a proposal was made in defining HS in elderly as “HS tarda” and subdividing it as late-onset and persistent HS tarda.