Autism spectrum disorder [A50] is a group ofdevelopmental disabilities that can cause significant social. communication

Autism spectrum disorder [A50] is a group ofdevelopmental disabilities that can cause significant social. communication, and behavioral difficulties for children. A group of investigators conducted a follow-up study to examine the risk ofASD and its three mutually exclusive and collectively exhaustive subtypes, namely: [‘1] Autistic disorder; [2} Asperger disordEr; and [3} Pervasive developmental disorder not otherwise specified {PUD-NUS} among children in Norway. From 2002 through 2007, they enrolled consenting mothers at approximately week ll] of pregnancy, and employed several resources to identify cases of A30 among their offspring. These resources included questionnaire screening at ages 3 and 5 years, professional and parental referral of children suspected of having A50, and linkage to the Norwegian Patient Register. At each questionnaire screening (at age 3, 5}, parents were asked questions about childhood medication use, sleeping habits, and several other factors. The study and follow-up ended on December 31, 200?. The table below presents the cumulative incidence of A50 over the study duration by year of birth: Years of Birth Cumulative incidence ofASD 2002 0.36% 2003 0.??% 2004 0.48% 2005 0.41% 2006 0.34% 2007 0.19% a] After browsing these results, your colleague states that these findings must represent a birth cohort effect, because the risk of AS!) in Norwegian children is greater among earlier birth cohorts than among later ones. Do you agree? Justify your answer.