Prevalence of Survival Without Major Comorbidities Among Adults Born Prematurely

Key PointsQuestionWhat is the prevalence of survival without major comorbidities in adulthood among persons born prematurely? FindingsIn this population-based cohort study of more than 2.5 million persons born in Sweden from 1973 to 1997, 54.6% of those born preterm (gestational age <37 weeks) and 22.3% of those born extremely preterm (22-27 weeks) were alive with no major comorbidities at ages 18 to 43 years, compared with 63.0% of those born full-term. The prevalences were statistically significantly lower in those born at earlier gestational ages vs full-term. MeaningAmong Swedish persons born prematurely, a large percentage survived into adulthood and had no major comorbidities. ImportancePreterm birth has been associated with cardiometabolic, respiratory, and neuropsychiatric disorders in adulthood. However, the prevalence of survival without any major comorbidities is unknown. ObjectiveTo determine the prevalence of survival without major comorbidities in adulthood among persons born preterm vs full-term. Design, Setting, and ParticipantsNational cohort study of all 2566699 persons born in Sweden from January 1, 1973, through December 31, 1997, who had gestational age data and who were followed up for survival and comorbidities through December 31, 2015 (ages 18-43 years). ExposuresGestational age at birth. Main Outcomes and MeasuresSurvival without major comorbidities among persons born extremely preterm (22-27 weeks), very preterm (28-33 weeks), late preterm (34-36 weeks), or early term (37-38 weeks), compared with full-term (39-41 weeks). Comorbidities were defined using the Adolescent and Young Adult Health Outcomes and Patient Experience (AYA HOPE) Comorbidity Index, which includes conditions that commonly manifest in adolescence or young adulthood, including neuropsychiatric disorders; and the Charlson Comorbidity Index (CCI), which includes major chronic disorders predictive of mortality in adulthood. Poisson regression was used to determine prevalence ratios and differences, adjusted for potential confounders. ResultsIn this study population, 48.6% were female, 5.8% were born preterm, and the median age at end of follow-up was 29.8 years (interquartile range, 12.6 years). Of all persons born preterm, 54.6% were alive with no AYA HOPE comorbidities at the end of follow-up. Further stratified, this prevalence was 22.3% for those born extremely preterm, 48.5% for very preterm, 58.0% for late preterm, 61.2% for early term, and 63.0% for full-term. These prevalences were significantly lower for earlier gestational ages vs full-term (eg, adjusted prevalence ratios: extremely preterm, 0.35 [95% CI, 0.33 to 0.36; P<.001]; all preterm, 0.86 [95% CI, 0.85 to 0.86; P<.001]; adjusted prevalence differences: extremely preterm, -0.41 [95% CI, -0.42 to -0.40; P<.001]; all preterm, -0.09 [95% CI, -0.09 to -0.09; P<.001]). Using the CCI, the corresponding prevalences were 73.1% (all preterm), 32.5% (extremely preterm), 66.4% (very preterm), 77.1% (late preterm), 80.4% (early term), and 81.8% (full-term) (adjusted prevalence ratios: extremely preterm, 0.39 [95% CI, 0.38 to 0.41; P<.001]; all preterm, 0.89 [95% CI, 0.89 to 0.89; P<.001]; adjusted prevalence differences: extremely preterm, -0.50 [95% CI, -0.51 to -0.49; P<.001]; all preterm, -0.09 [95% CI, -0.09 to -0.09; P<.001]). Conclusions and RelevanceAmong persons born preterm in Sweden between 1973 and 1997, the majority survived to early to mid-adulthood without major comorbidities. However, outcomes were worse for those born extremely preterm. This cohort study uses data from the Swedish Birth Registry to determine the prevalence of survival without major comorbidities in adulthood among persons born preterm vs full-term in Sweden between 1973 and 1997.