1. Department of Pediatrics, Okayama University Academic Field of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama 700-8558, Japan
2. Department of Pediatrics, Kawasaki Medical School, Kurashiki 701-0192, Japan
3. Department of Epidemiology, Okayama University Academic Field of Medicine, Dentistry, and Pharmaceutical Sciences, Okayama 700-8558, Japan