Jakob Øster was a paediatrician and school doctor from Randers, Denmark. In 1968, he published a study about the incidence of phimosis, tight prepuce, and smegma in various age-groups. Øster (1968) found that the incidence of fusion of the foreskin with the glans penis steadily declines with increasing age and foreskin retractability increases with age.
- Øster, J. (1968): Further Date of the Foreskin: Incidence of Preputial Adhesions, Phimosis, and Smegma among Danish Schoolboys, in: Arch Dis Child. 43:200-203, PMID, PMC, DOI. Retrieved 8 November 2019.