Study Suggests Individuals Born Preterm Are More Likely to Have Lower Incomes in Adulthood

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In a time of increasing income disparity, researchers are beginning to discover that preterm birth (PTB) may have an impact on a person’s financial status once they reach adulthood. In a study published by the JAMA Network, researchers found that individuals born preterm experience lower income levels in adulthood compared to those born full-term. Additionally, this finding became more noticeable in people from economically disadvantaged families, suggesting that family socioeconomic status at birth plays a major role in shaping the financial future of this demographic, according to the study authors.¹

“To our knowledge, this is the first study to use multigenerational linked data to examine the association of PTB with the socioeconomic position of individuals relative to their parents and the role of family SES as a modifying factor,” wrote the authors of the study. “This population-based study showed that preterm born individuals had lower annual income during young adulthood than those born at full term, with greater differences for those with lower GA. The magnitude of these differences was slightly larger for those belonging to families with low SES. Furthermore, PTB was associated with lower upward mobility and higher downward mobility, particularly for those born at less than 32 weeks’ GA.”

In order to achieve accurate results, the study linked population-level health, demographic, and income data across generations to create a comprehensive dataset. Through the utilization of data on birth records, income tax filing, and vital statistics, the researchers followed a group of individuals born in Canada between 1990-1996 for a 28-year period, effectively ending in 2018. Data confidentiality was maintained throughout the study, with it being accessed through a secure server at Statistics Canada.

Regarding exposure, the authors of the study classified PTB as birth before 37 completed weeks of gestation, and early and full-term birth was defined as birth at 37 to 41 weeks of gestation. PTB was broken into four groups, which were categorized as extremely preterm (22-27 weeks), very preterm (28-31 weeks), moderately preterm (32-33 weeks), and late preterm (34-36 weeks).

Additional statistics included in the study were matching variables such as sex, birth plurality, province of birth, birth year, parental age at birth, maternal marital status, maternal parity, and parental place of birth. Further, family income at birth, child income in adulthood, and intergenerational income mobility were measured as well. Of 2,729,400 live births recorded in Canada between 1990-1996, the PTB rate after study adjustments was 6.9% (5.4% born at 34-36 weeks, 0.7% born at 32-33 weeks, 0.5% born at 28-31 weeks, and 0.2% born at 24-27 weeks).

The results suggest that PTB individuals, especially those with a lower gestational age, are less likely to improve their socioeconomic status (SES), with the data suggesting that they were more likely to find their SES downgraded. The relative risk for the association between PTB and upward mobility among children of families in the lowest income quintile was 0.92 (95% CI, 0.89-0.96), with differences increasing in lower GA groups (24-27 weeks’ GA: RR, 0.61 [95% CI, 0.48-0.77]).

Regarding downward mobility, results indicated that PTB individuals, especially those born very or extremely preterm in economically disadvantaged families, had reduced potential for social mobility. Those in the lower two groups who also grew up with higher income families faced greater risks of downward mobility compared to full term–born individuals, according to the investigators.

In terms of limitations, the authors suggested that future studies needed to improve on their research in multiple areas. First, 30% of births in Canada that occurred during the study were omitted. Additionally, some were excluded due to tax records being unavailable. The authors suggest that income might not fully capture all aspects of SES or intergenerational mobility as well.¹

“This population-based intergenerational cohort study suggests that PTB was associated with lower income during young adulthood, especially with lower GA, with more differences for children of families near the bottom of income distribution. Furthermore, preterm-born individuals, particularly those born very or extremely preterm in economically disadvantaged families, had less potential for social mobility. Future studies should consider longer durations of follow-up to examine intergenerational income mobility when children are in their 30s and 40s. Studies should also consider other aspects of SES, such as education and occupation,” the study authors concluded.

Reference

Preterm Birth, Family Income, and Intergenerational Income Mobility. JAMA Network. June 10, 2024. Accessed June 12, 2024. https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2819745