OBJECTIVE: Previous studies have demonstrated an increased risk for attention-deficit/hyperactivity disorder (ADHD) in follow-up studies of preterm survivors from NICUs. In this study we analyzed the effect of moderate as well as extreme preterm birth on the risk for ADHD in school age, taking into account genetic, perinatal, and socioeconomic confounders. METHODS: Register study in a Swedish national cohort of 1 180 616 children born between 1987 and 2000, followed up for ADHD medication in 2006 at the age of 6 to 19 years. Logistic regression was used to test hypotheses. A within-mother-between-pregnancy design was used to estimate the importance of genetic confounding in a subpopulation of offspring (N = 34 334) of mothers who had given birth to preterm (≤34 weeks) as well as term infants. RESULTS: There was a stepwise increase in odds ratios for ADHD medication with increasing degree of immaturity at birth; from 2.1 (1.4–2.7) for 23 to 28 weeks' gestation, to 1.6 (1.4–1.7) for 29 to 32 weeks', 1.4 (1.2–1.7) for 33 to 34 weeks', 1.3 (1.1–1.4) for 35 to 36 weeks', and 1.1 (1.1–1.2) for 37 to 38 weeks' gestation compared with infants born at 39 to 41 weeks' gestation in the fully adjusted model. The odds ratios for the within-mother-between-pregnancy analysis were very similar. Low maternal education increased the effect of moderate, but not extreme, preterm birth on the risk for ADHD. CONCLUSION: Preterm and early term birth increases the risk of ADHD by degree of immaturity. This main effect is not explained by genetic, perinatal, or socioeconomic confounding, but socioeconomic context modifies the risk of ADHD in moderately preterm births.

OBJECTIVE. Increasing numbers of infants born preterm survive into adulthood. In this study, we analyzed the effect of having been born preterm on disability and vocational success in young adults. METHODS. A Swedish national cohort of 522310 infants born in 1973–1979 were followed up for disabilities and income in national registers in 2002 at the age of 23 to 29. Hypotheses were tested in multivariate analysis with logistic regression models on the log scale for dichotomized outcomes and linear regression for continuous variables. RESULTS. There was a stepwise increase in disability in young adulthood with increasing degree of preterm birth. A total of 13.2% of children born at 24 to 28 weeks' gestation and 5.6% born at 29 to 32 weeks' gestation received economic assistance from society because of handicap or persistent illness, which is which is equivalent to nearly 4 times the risk of those born at term after adjustment for socioeconomic and perinatal confounders. Moderate (33–36 weeks' gestation) and marginal (37–38 weeks' gestation) preterm birth also carried significantly increased risks for disability and were responsible for 74% of the total disability associated with preterm birth. Preterm birth was associated with a lower chance of completing a university education and a lower net salary in a stepwise manner. The total economic gain for Swedish society, in terms of taxes and decreased costs for benefits, if all long-term effects of preterm birth could have been prevented in the birth cohorts in this study, would have amounted to 65 million euros in 2002 alone. CONCLUSIONS. The majority of adults who were born very preterm lived an independent and self-supportive life. Moderately preterm birth carries a considerable risk for long-term impairment. There are strong economic incentives for secondary prevention of disability associated with preterm birth.