Time trends in incidence of pilonidal sinus disease from 1996 to 2021: A Danish population-based cohort study.

Aim: Pilonidal sinus disease (PSD) is a common condition, but no data on disease occurrence exist outside highly selected settings. The aim of this study was to assess time trends in the incidence of PSD in a nationwide setting.

Method: Using data from nationwide Danish registries, we identified 48 247 patients recorded with diagnostic or surgical procedure codes representing PSD between 1996 and 2021. We stratified by sex and computed the age-adjusted and age-specific incidence rate, comparing 5-year intervals with the incidence rate ratio (IRR).

Results: The overall incidence of PSD increased from 26.1 to 39.6/100 000 person-years (PY) from the period 1996-2000 to the period 2016-2021 (IRR 1.52, 95% CI 0.78-2.94). The incidence increased from 35.8 to 56.9/100 000 PY (IRR 1.59, 95% CI 0.52-4.89) in male patients and from 16.4 to 22.5/100 000 PY (IRR 1.37, 95% CI 0.68-2.76) in female patients. The peak of age-specific incidence was 215.7/100 000 PY (95% CI 206.1-245.4) among 20-year-old men and 107.9/100.000 PY (95% CI 100.0-114.0) among 18-year-old women. Over the study period, the median age at first hospital contact decreased from 27 years [interquartile range (IQR) 22-34 years) to 25 years (IQR 20-34 years) in men but remained stable around 23 years (IQR 18-32 years) in women. However, for both sexes, the highest increase in incidence was seen in early adolescence.

Conclusion: The incidence of PSD has increased significantly over the last decades. The increase is driven primarily by men and boys, with the highest increase in incidence seen in early adolescence. The increased burden of disease is not reflected in the literature, and more studies are warranted to understand the drivers of this development.