Study population
The COhort for Childhood Origin of Asthma and Allergic diseases (COCOA) is a prospective, general population-based birth cohort study designed to investigate the individual and interactive effects of genetics, perinatal environment, maternal lifestyle, and psychosocial stress of mother and child on pediatric susceptibility to allergic diseases.17 Regular follow-up visits involving physician examination and self-report questionnaires concerning the environment were conducted at at least 26 weeks gestation, at birth, 6 months, 1 year, and then annually.18 From yearly follow-ups of pediatric allergists, we collected information on the allergic symptoms, diagnosis, and prescribed treatment. Among the 3,102 pairs enrolled in the COCOA cohort, 1,636 children were aged over 6 years. The 706 patients lacking clinical and laboratory data were excluded, leaving 930 patients to be analyzed (Figure E1). The average age of the patients was 8.02 years, and 52.7% were male. Significant differences in birth weight, breastfeeding rates, and antibiotic use before 1 year of age were observed between the included and excluded groups (Table E1).
Allergic diseases including PFAS were diagnosed by a physician or typical symptoms (itching, sore throat, or swelling) in the lips, mouth, and throat immediately after eating fresh fruits or vegetables by parental questionnaire. If PFAS was suspected, the trigger of PFAS was also investigated.
The study was approved by the Institutional Review Boards of Asan Medical Center (IRB No. 2008–0616), Samsung Medical Center (IRB No. 2009-02-021), Severance Medical Center (IRB No. 4-2008–0588), CHA Gangnam Medical Center (IRB No. 2010–010), and Seoul National University Hospital (IRB No. H-1401-086-550) before initiation. Written informed consent was obtained from each patient’s parents or guardians before the interview, confirmed by each IRB.