Elevated risk of attention deficit hyperactivity disorder (ADHD) in Japanese children with higher genetic susceptibility to ADHD with a birth weight under 2000 g

Table 4 Association of birth weight categories and genetic risk with inattention and hyperactivity scores among Japanese children at age 8–9 years (N=659) (a total of 137 children with missing information on PRS was excluded from this analysis)

Birth weight and genetic risk of ADHD	Rate ratio (95% confidence intervals)
Birth weight and genetic risk of ADHD	Model 1^†	Model 2^‡	Model 3^§
Inattention symptoms
Normal birth weight
Low risk (ref.)	1.00	1.00	1.00
High risk	0.96 (0.81–1.13)	0.95 (0.81–1.12)	0.96 (0.82–1.13)
Birth weight 2000–2499 g
Low risk	0.89 (0.58–1.35)	1.02 (0.67–1.56)	1.02 (0.67–1.56)
High risk	0.93 (0.62–1.39)	0.96 (0.62–1.50)	0.97 (0.62–1.50)
Birth weight <2000 g
Low risk	1.21 (0.82–1.77)	1.22 (0.80–1.84)	1.19 (0.78–1.81)
High risk	1.70 (1.02–2.83)*	1.59 (1.09–2.31)*	1.56 (1.07–2.27)*
Hyperactivity symptoms
Normal birth weight
Low risk (ref.)	1.00	1.00	1.00
High risk	1.02 (0.81–1.29)	1.04 (0.84–1.27)	1.03 (0.84–1.27)
Birth weight 2000–2499 g
Low risk	0.86 (0.50–1.49)	1.10 (0.62–1.93)	1.10 (0.63–1.91)
High risk	0.68 (0.36–1.28)	0.64 (0.37–1.11)	0.63 (0.37–1.08)
Birth weight <2000 g
Low risk	1.56 (0.73–3.31)	1.65 (0.75–3.65)	1.64 (0.77–3.48)
High risk	2.10 (1.10–3.98)*	1.94 (1.19–3.17)**	1.87 (1.14–3.06)*

Note: Normal birth weight was defined as birth weight ≥ 2500 g; ref., reference category; values in bold show statistical significance; **p<0.01; *p<0.05
^†Model 1 was adjusted for variations in survey time only
^‡Model 2 additionally adjusted for gender of child, parity, maternal age, education, pre-pregnancy body mass index, pre-pregnancy smoking status, and alcohol intake
^§Model 3 additionally adjusted for father’s age at birth and household annual income

ISSN: 1741-7015