A Longitudinal Investigation of Co-Occurring Conditions in Children with Autism Spectrum Disorder

Introduction: 
Children with autism spectrum disorder (ASD) are generally more likely to develop co-occurring conditions (COCs) than their typically developing peers. However, the difference in the prevalence of individual co-occurring conditions is still a topic of research. One of reasons this is a non-trivial research topic is that the prevalence and diagnostic criteria of both ASD and many COCs have changed over time. Few studies have been able to evaluate how the prevalence of COCs and ASD have changed over time within the same population. This knowledge gap complicates the task of tailoring diagnostic screening recommendations for those with ASD.

Materials and Methods: 
The Independent Healthcare Research Database consists of Florida Medicaid claims and eligibility data files generated from 1990 to 2012 that have been de-identified. From this database healthcare claims for children born between 1990 and 2001 were evaluated using odds ratios to compare the prevalence of co-occurring conditions and determine relative significance between those with ASD and those without over time. Only individuals who were continuously enrolled in the Florida Medicaid system from birth until at least age eight with at least one claim in that time period were included. Prevalence of examined COC groupings were investigated as a collective cohort and by birth year. The timeline of COC development was evaluated using the collective cohort by date of the first claim with each diagnosis.

Results, Conclusions, and Discussions: 
A collective cohort of 2381 children with ASD and 310273 TD children were identified, with each birth year cohort being of relatively equal size. This cohort’s relevance is established by matching CDC national estimates of ASD prevalence and sex demographics for the time period. Within the study period, children with ASD had, on average, a higher prevalence of COCs in all examined categories. Prevalence within each COC category showed little change between years, with few exceptions. These findings may help to inform screening procedures for those with ASD.