Layton TJ, et al. - Using data from 2007 through 2015 from a large insurance database, comparisons were made with regard to rate of attention deficit–hyperactivity disorder (ADHD) diagnosis between children born in August vs children born in September in states with and states without the requirement that children be 5 years old by September 1 for enrollment in kindergarten. According to findings, higher rates of diagnosis and treatment of ADHD were reported among children born in August than among children born in September in states with a September 1 cutoff for kindergarten entry.

Methods

• According to diagnosis codes from the International Classification of Diseases, 9th Revision, researchers determined ADHD diagnosis.
• Using prescription records, they compared ADHD treatment between children born in August and children born in September in states with and states without the cutoff date of September 1.

Results

• A total of 407,846 children in all U.S. states who were born in the period from 2007 through 2009 and were followed through December 2015 were included.
• Among children in states with a September 1 cutoff, the observed rate of claims-based ADHD diagnosis was 85.1 per 10,000 children (309 cases among 36,319 children; 95% confidence interval [CI], 75.6 to 94.2) and 63.6 per 10,000 children (225 cases among 35,353 children; 95% CI, 55.4 to 71.9) among those born in August and among those born in September, respectively, an absolute difference of 21.5 per 10,000 children (95% CI, 8.8 to 34.0); the corresponding difference in states without the September 1 cutoff was 8.9 per 10,000 children (95% CI, −14.9 to 20.8).
• Among those born in August and among those born in September, the observed rate of ADHD treatment was 52.9 per 10,000 children (192 of 36,319 children; 95% CI, 45.4 to 60.3) and 40.4 per 10,000 children (143 of 35,353 children; 95% CI, 33.8 to 47.1), respectively, an absolute difference of 12.5 per 10,000 children (95% CI, 2.43 to 22.4).
• For other month-to-month comparisons and in states with non-September cutoff dates for starting kindergarten, these differences were not observed.
• Rates of asthma, diabetes, or obesity did not differ remarkably between August-born and September-born children in states with a September 1 cutoff.