Figure 1
A schematic illustration of the participant selection process that was used in the present study. Of a total of 1,125,691 participants, 158,363 children (≤14 years old) had a history of asthma from 2002 through 2013. Among them, 2,326 participants underwent tonsillectomy from 2003 through 2010. The tonsillectomy participants were matched 1:4 with a control I group of participants who did not undergo tonsillectomy for age, sex, income, and region (study I) and a control II group for age, sex, income, region, and preoperative asthma history (study II). In study II, unmatched tonsillectomy participants were excluded (n = 46). Finally, 2,326 tonsillectomy participants and 9,304 control I participants were included in study I, and 2,280 tonsillectomy participants and 9,120 control II participants were included in study II.
