Limitations and Implications
This is the fourth time Minnesota data has been included in findings from the ADDM Network and the second time we have included 4-year-old as well as 8-year-old prevalence. Compared to 2018 estimates, overall prevalence of ASD for 8-year-old children was similar to or slightly higher than in 2020. Overall prevalence of ASD among 4-year-olds in 2020 was lower than prevalence among 4-year-olds in 2018. The portions of Ramsey and Hennepin counties included in prevalence estimates differed in 2018 and 2020, which may have impacted prevalence estimates.
In Minnesota, there are differences between the proportions of males and females identified with ASD, with more males than females in both the 8- and 4-year-old groups. This is consistent with previous estimates, both in Minnesota and across the ADDM network. (Note: the ADDM project only collects data on male and female sex as indicated in records and does not include gender identification information.)
In Minnesota, we identify ASD much later than when first concerns are reported. The median age of the first ASD diagnosis for 8-year-olds was 4 years and 11 months, which was the latest age across the ADDM Network. We found that 4-year-old children are being identified with ASD at 1.5 times the rate of 8-year-old children, which indicates that identification is happening more frequently at earlier ages. Nonetheless, the late age of identification is concerning due to the critical importance of early identification and intervention. Many states, including MN, have invested in early intervention to help children and families gain access to early intervention services. For example, Minnesota’s Early Intensive Developmental and Behavioral Intervention (EIDBI) Benefit provides early intensive intervention for people with ASD and related conditions. To learn more about the EIDBI benefit follow this link:
We found varying prevalence rates across racial and ethnic groups in Minnesota. The small number of children in some of these groups makes it difficult to determine whether the rates of children with ASD truly are different across groups. When differences are found, it is important to focus on general health disparities that may influence these differences.
We found that of the 8-year-old children who had IQ information in their records, 32% had an intellectual disability. Among 4-year-old children with IQ information, 62% had an intellectual disability. The higher rate of intellectual disability in the younger group is not unexpected, as children with ASD with developmental delays are often identified earlier than children with ASD without developmental delays.
Minnesota experienced marked reductions in ASD evaluations and identifications with the onset of the COVID-19 pandemic in March 2020. These reductions persisted through the end of 2020 in Minnesota and two other states, while 8 ADDM sites showed a recovery of evaluations and identifications to close to pre-pandemic levels.
The findings in this report reflect a small number of children concentrated in a large metropolitan area and may not generalize to other parts of Minnesota.
The numbers of 4- and 8-year-old children with ASD from some racial/ethnic groups are small, and their prevalence estimates will be less precise than estimates for larger-sized populations. Confidence intervals show the range in which we are 95% confident that true prevalence lies, and a larger confidence interval means less precision (e.g., 14.4–25.0 for Asian/Pacific Islander 4-year-old children). This tells us we should use caution before drawing conclusions about differences between some groups.
MN-ADDM reviewed records from participating public school special education programs but did not review private school education records or all charter school education records within our geographic area. Similarly, if a child was identified with ASD in a clinic outside of those included in MN-ADDM’s geographic area, their health records may not have been captured. Incomplete information could lead to misclassifying children’s cognitive ability, overestimating the age when they were first evaluated or when ASD was identified, or failing to capture that the children were identified as having ASD.