Child Health Evaluative Sciences, The Hospital for Sick Children, Toronto, Ontario, Canada.
Department of Epidemiology and Prevention, Wake Forest University School of Medicine, Winston-Salem, North Carolina.
JAMA Netw Open. 2024 Jun 3;7(6):e2415921. doi: 10.1001/jamanetworkopen.2024.15921.
Preterm birth (PTB) has been associated with lower income in adulthood, but associations with intergenerational income mobility and the role of family socioeconomic status (SES) as modifying factor are unclear.
To assess whether the association between PTB and income differs according to family SES at birth and to assess the association between PTB and intergenerational income mobility.
DESIGN, SETTING, AND PARTICIPANTS: This study comprised a matched cohort of live births in Canada between January 1, 1990, and December 31, 1996, with follow-up until December 31, 2018. Statistical analysis was performed between May 2023 and March 2024.
Preterm birth, defined as birth between 24 and 37 weeks' gestational age (with gestational age subcategories of 34-36, 32-33, 28-31, and 24-27 weeks) vs early and full term births (gestational age, 37-41 weeks).
Associations between PTB and annual adulthood income in 2018 Canadian dollars were assessed overall (current exhange rate: $1 = CAD $1.37) and stratified by family income quintiles, using generalized estimating equation regression models. Associations between PTB and percentile rank change (ie, difference between the rank of individuals and their parents in the income distribution within their respective generations) and upward or downward mobility (based on income quintile) were assessed using linear and multinomial logistic regressions, respectively.
Of 1.6 million included births (51.1% boys and 48.9% girls), 6.9% infants were born preterm (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). After matching on baseline characteristics (eg, sex, province of birth, and parental demographics) and adjusting for age and period effects, PTB was associated with lower annual income (mean difference, CAD -$687 [95% CI, -$788 to -$586]; 3% lower per year), and the differences were greater among those belonging to families in the lowest family SES quintile (mean difference, CAD -$807 [95% CI, -$998 to -$617]; 5% lower per year). Preterm birth was also associated with lower upward mobility and higher downward mobility, particularly for those born earlier than 31 weeks' gestational age (24-27 weeks: mean difference in percentile rank change, -8.7 percentile points [95% CI, -10.5 to -6.8 percentile points]).
In this population-based matched cohort study, PTB was associated with lower adulthood income, lower upward social mobility, and higher downward mobility, with greater differences among those belonging to economically disadvantaged families. Interventions to optimize socioeconomic outcomes of preterm-born individuals would need to define target population considering SES.
早产（PTB）与成年后收入较低有关，但与代际收入流动性的关联以及家庭社会经济地位（SES）作为调节因素的作用尚不清楚。
评估 PTB 与出生时家庭 SES 之间的关联是否存在差异，并评估 PTB 与代际收入流动性之间的关联。
设计、地点和参与者：这是一项在加拿大进行的匹配队列研究，纳入了 1990 年 1 月 1 日至 1996 年 12 月 31 日期间出生的活产儿，并随访至 2018 年 12 月 31 日。统计分析于 2023 年 5 月至 2024 年 3 月进行。
早产定义为出生于 24 至 37 孕周（包括 34-36 周、32-33 周、28-31 周和 24-27 周的亚组）与早期和足月出生（孕周 37-41 周）之间的差异。
使用广义估计方程回归模型，总体评估（当前汇率：1 美元=1.37 加元）和按家庭收入五分位数分层评估 PTB 与 2018 年加拿大元成年后收入之间的关联。使用线性和多项逻辑回归分别评估 PTB 与百分位秩变化（即个体与其父母在各自代际收入分布中的等级差异）和向上或向下流动（基于五分位数）之间的关联。
在纳入的 160 万例分娩中（51.1%为男孩，48.9%为女孩），有 6.9%的婴儿早产（5.4%出生于 34-36 孕周，0.7%出生于 32-33 孕周，0.5%出生于 28-31 孕周，0.2%出生于 24-27 孕周）。在对基线特征（如性别、出生地和父母人口统计学特征）进行匹配，并调整年龄和时期效应后，PTB 与较低的年收入相关（平均差异，CAD-687 美元[95%CI，-788 美元至-586 美元]；每年低 3%），而在 SES 最低五分位数家庭中，差异更大（平均差异，CAD-807 美元[95%CI，-998 美元至-617 美元]；每年低 5%）。PTB 也与较低的向上流动和较高的向下流动相关，尤其是对于那些早于 31 周胎龄（24-27 周）出生的婴儿（平均差异，百分位秩变化，-8.7 个百分点[95%CI，-10.5 个百分点至-6.8 个百分点]）。
在这项基于人群的匹配队列研究中，PTB 与成年后收入较低、向上社会流动性较低和向下流动性较高有关，而在经济弱势群体中差异更大。为优化早产儿的社会经济结局，需要根据 SES 来确定目标人群。
