Abstract Aim Children with autism spectrum disorder (ASD) are more likely to have sleep problems. Few studies have investigated the relationship between sleep problems and blood melatonin and ferritin levels. The objective of this study was to determine the correlation between sleep problems and morning serum melatonin and ferritin levels, and the differences in serum melatonin and ferritin levels between children with ASD and those without ASD. Methods Four years of data from population‐based 5‐year‐old checkups were referenced. Fifty‐five children were divided into the ASD group ( N = 45) and the non‐ASD group ( N = 10). Blood samples were collected at 8:30 a.m. The Japanese Sleep Questionnaire for Preschoolers (JSQP) was used to assess sleep problems. Correlation analysis, the Mann–Whitney U test, and multiple regression analysis were used. Results In the ASD group, the score of Sleep habit was significantly correlated with the serum ferritin level ( ρ = 0.496, p < 0.001). No significant regression equation was found. However, the partial correlation coefficient calculated indicated a significant value between the score of Insomnia or Circadian rhythm disorder and serum melatonin level ( β = 0.502, p < 0.05), and the score of Sleep habit and the serum ferritin level ( β = 0.546 p < 0.01). The serum ferritin level in the ASD group (23.48 ± 9.14 ng/mL) was significantly higher than in the non‐ASD group (14.84 ± 7.09 ng/mL) ( p < 0.05). Conclusion This study indicated that children with ASD were more likely to have some sleep problems and higher morning serum ferritin levels than those without ASD. Further research is recommended on the correlation between sleep problems and morning serum melatonin and ferritin levels.
Terui et al. (2026) studied this question.