1. Department of Life, Health and Environmental Sciences; University of L'Aquila; L'Aquila Italy
2. Epidemiologic and Biostatistics Unit; AUSL; Teramo Italy
3. Department of Public Health; ASREM Molise; Campobasso Italy
4. Department of Pediatrics; University of Perugia; Perugia Italy
5. Department of Pediatrics; University of Chieti; Chieti Italy