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Summary: Background: Roughly more than one in six adults worldwide suffer from psychiatric conditions. Sporadic studies have associated parental psychiatric disorders with autism spectrum disorder in offspring. Comprehensively examining the association between parental psychiatric disorders and offspring autism spectrum disorder is needed to guide health policies, and to inform etiologic studies. Methods: We included all children born in Sweden and Finland 1997–2016. Diagnoses were clinically ascertained from National Registers through 2017. We calculated adjusted hazard ratios (aHRs) and 95% confidence intervals (CIs) for autism spectrum disorder in offspring of fathers and mothers with psychiatric disorders, in both parents jointly and across co-occurring conditions. Findings: Among 2,505,842 children, 33,612 were diagnosed with autism spectrum disorder, of which 20% had a parent with psychiatric disorders. The risk of autism spectrum disorder was increased across all psychiatric disorders in fathers (Sweden: aHR = 2.02, 95% CI = 1.92–2.12; Finland: aHR = 1.63, 95% CI = 1.50–1.77), mothers (Sweden: aHR = 2.34, 95% CI = 2.24–2.43; Finland aHR = 2.12, 95% CI = 1.92–2.28), or both parents (Sweden: aHR = 3.76, 95% CI = 3.48–4.07; Finland aHR = 3.61, 95% CI = 3.20–4.07), compared to neither parents. Co-occurrence of parental psychiatric disorders further increased risk (e.g., Sweden: for one, two or ≥three different diagnostic categories compared to no diagnosis, in fathers aHR = 1.81, 2.07, 2.52; in mothers aHR = 2.05, 2.63, 3.57). Interpretation: Psychiatric disorders in both parents conveyed the highest risk of offspring autism spectrum disorder, followed by mothers and then fathers. The risk increased with number of co-occurring disorders. All parental psychiatric disorders were associated with increased the risk of autism spectrum disorder. To reliably assess the risk of autism spectrum disorder in children, a comprehensive history incorporating the full range of parental psychiatric disorders is needed beyond solely focusing on familial autism spectrum disorder. Funding: Swedish-Research-Council-2021-0214.

Summary: Background: Preterm birth is associated with increased risk of childhood infections. Whether this risk persists into adulthood is unknown and limited information is available on risk patterns across the full range of gestational ages. Methods: In this longitudinal, register-based, cohort study, we linked individual-level data on all individuals born in Norway (January 01, 1967–December 31, 2016) to nationwide hospital data (January 01, 2008–December 31, 2017). Gestational age was categorised as 23–27, 28–31, 32–33, 34–36, 37–38, 39–41, and 42–44 completed weeks. The analyses were stratified by age at follow-up: 0–11 months and 1–5, 6–14, 15–29, and 30–50 years. The primary outcome was hospitalisation due to any infectious disease, with major infectious disease groups as secondary outcomes. Adjusted hospitalisation rate ratios (RRs) for any infection and infectious disease groups were estimated using negative binomial regression. Models were adjusted for year of birth, maternal age at birth, parity, and sex, and included an offset parameter adjusted for person-time at risk. Findings: Among 2,695,830 individuals with 313,940 hospitalisations for infections, we found a pattern of higher hospitalisation risk in lower gestational age groups, which was the strongest in childhood but still evident in adulthood. Comparing those born very preterm (28–31) and late preterm (34–36) to full-term (39–41 weeks), RRs (95% confidence interval) for hospitalisation for any infectious disease at ages 1–5 were 3.3 (3.0–3.7) and 1.7 (1.6–1.8), respectively. At 30–50 years, the corresponding estimates were 1.4 (1.2–1.7) and 1.2 (1.1–1.3). The patterns were similar for the infectious disease groups, including bacterial and viral infections, respiratory tract infections (RTIs), and infections not attributable to RTIs. Interpretation: Increasing risk of hospitalisations for infections in lower gestational age groups was most prominent in children but still evident in adolescents and adults. Possible mechanisms and groups that could benefit from vaccinations and other prevention strategies should be investigated. Funding: St. Olav's University Hospital and Norwegian University of Science and Technology, Norwegian Research Council, Liaison Committee for education, research and innovation in Central Norway, European Commission, Academy of Finland, Sigrid Jusélius Foundation, Foundation for Pediatric Research, and Signe and Ane Gyllenberg Foundation.