A large-scale Nordic study revealed that women born preterm faced significantly higher suicide mortality risks compared with full-term peers, while showing no similar association among men.
In the research, published in BMC Medicine, investigators analyzed data from over 6.9 million individuals across Denmark, Finland, Norway, and Sweden, following participants from age 15 to 50 years. During follow-up, 29,758 participants (0.43%) died from external causes: 7,850 (26.4%) from transport accidents, 11,320 (38.0%) from suicide, and 7,785 (26.2%) from drugs or alcohol.
Women born very or moderately preterm (23 to 33 weeks gestation) demonstrated a 76% higher risk of suicide mortality compared with women born full term (adjusted hazard ratio [HR] = 1.76, 95% confidence interval [CI] = 1.34–2.32). The study defined gestational age categories as "very/moderately preterm" (23 to 33 weeks), "late preterm" (34 to 36 weeks), "early term" (37 to 38 weeks), "full term" (39 to 41 weeks), and "postterm" (42 to 44 weeks).
The investigators identified 370,492 preterm births (< 37 weeks), comprising 5.3% to 5.6% of each country's study population. Among these, 1.3% to 1.4% of them were very/moderately preterm births, and 3.9% to 4.3% of them were late preterm births.
Both men and women born preterm showed higher mortality rates from drugs or alcohol. For very or moderately preterm births, the adjusted HRs were 1.23 (95% CI = 0.99–1.53) for men and 1.53 (95% CI = 0.97–2.41) for women. Late preterm births showed HRs of 1.29 (95% CI = 1.16–1.45) for men and 1.35 (95% CI = 1.07–1.71) for women.
Mortality rates increased steeply during late adolescence for all outcomes. During adulthood, rates leveled off for external causes overall and suicide but declined gradually for transport accidents. Drug- or alcohol-related mortality continued increasing with age among women but declined from around age 30 years among men.
The study excluded 224,703 (3.1%) individuals with missing data on gestational age, birthweight, sex, birth order, and maternal age. An additional 8,857 (0.1%) cases fell outside the 23 to 44 weeks gestational range, and 19,812 (0.3%) showed unlikely combinations of birthweight and gestational age.
Data validation from previous studies showed 90%, 81%, and 88% agreement between registered cause of death and expert panel reviews for suicide in Denmark, Norway, and Sweden, respectively. The investigators conducted sensitivity analyses, including deaths of unknown intent, which yielded similar results.
The findings remained consistent when analyses were restricted to individuals born after 1987, suggesting that improved survival rates for preterm infants did not significantly impact the observed associations.
Country-specific variations emerged, with Finland showing no clear association between preterm birth and suicide risk in women, while patterns remained similar across Denmark, Norway, and Sweden.
The study's results highlighted the importance of long-term follow-up in individuals born preterm, particularly regarding mental health outcomes in women.
The authors declared having no competing interests.
