Incidence of tonsillectomy in Denmark, 1980 to 2001.

Background: Tonsillectomy is one of the most frequent operations performed on children and young adults, but little is known regarding its distribution by age, sex, and calendar period.

Methods: We designed a population-based cohort study including all Danish residents from 1980 to 2001 to describe national incidence figures for tonsillectomy. Persons undergoing tonsillectomy were identified in the Danish National Patient Registry and from the Danish Health Security System. Overall, the cohort consisted of 6.3 million persons, who were followed up for 106.9 million person-years.

Results: During the study period 153,212 patients had tonsillectomies, comprising 84,831 females and 68,381 males. The age-specific incidence of tonsillectomy peaked at 4 years of age for both boys and girls, with 9.7 and 6.9 tonsillectomies per 1000 person-years, respectively. A second peak emerged during teenage years in both sexes, being highest among girls with 8.6 tonsillectomies per 1000 person-years at 16 years of age and 3.1 tonsillectomies per 1000 person-years among 17-year-old boys. The cumulative risk of tonsillectomy during the first 20 years of life increased from 7.9% among females and 6.0% among males in 1980 to 9.2% and 7.7%, respectively, in 2001. Over 90% of the patients less than 20 years of age registered at hospital with chronic disease of the tonsils had tonsillectomies within a year.

Conclusions: The incidence of tonsillectomy revealed significant gender differences. Furthermore, 2 incidence peaks emerged at age 4 years and age 16-17 years. The second peak in adolescence was particularly pronounced for females and is unexplained.