Catalano Ralph, Bruckner Tim A, Gemmill Alison, Casey Joan A, Margerison Claire, Hartig Terry
School of Public Health, University of California, Berkeley, Berkeley, CA, USA.
Program in Public Health and Center for Population, Inequality and Policy, University of California, Irvine, Irvine, CA, USA.
Evol Med Public Health. 2023 Jul 19;11(1):244-250. doi: 10.1093/emph/eoad018. eCollection 2023.
Selection predicts that population stressors raise the standard for how quickly fetuses must grow to avoid spontaneous abortion. Tests of this prediction must use indirect indicators of fetal loss in birth cohorts because vital statistics systems typically register fetal deaths at the 20th week of gestation or later, well after most have occurred. We argue that tests of selection would make greater progress if researchers adopted an indicator of selection against slow-growing fetuses that followed from theory, allowed sex-specific tests and used readily available data. We propose such an indicator and assess its validity as a dependent variable by comparing its values among monthly birth cohorts before, and during, the first 10 months of the COVID-19 pandemic in Sweden.
We apply Box-Jenkins methods to 50 pre-pandemic birth cohorts (i.e., December 2016 through January 2020) and use the resulting transfer functions to predict counterfactual values in our suggested indicator for selection for ten subsequent birth cohorts beginning in February 2020. We then plot all 60 residual values as well as their 95% detection interval. If birth cohorts in gestation at the onset of the pandemic lost more slow-growing fetuses than expected from history, more than one of the last 10 (i.e. pandemic-exposed) residuals would fall below the detection interval.
Four of the last 10 residuals of our indicator for males and for females fell below the 95% detection interval.
Consistent with selection , Swedish birth cohorts in gestation at the outset of the COVID-19 pandemic included fewer than expected infants who grew slowly .
选择理论预测，群体压力源会提高胎儿为避免自然流产所需的生长速度标准。由于生命统计系统通常在妊娠第20周或更晚才记录胎儿死亡情况，而此时大多数自然流产已经发生，因此对这一预测的检验必须使用出生队列中胎儿丢失的间接指标。我们认为，如果研究人员采用一个从理论推导得出的、针对生长缓慢胎儿的选择指标，允许进行性别特异性检验，并使用现成的数据，那么对选择理论的检验将会取得更大进展。我们提出了这样一个指标，并通过比较瑞典在新冠疫情前10个月、疫情期间各月出生队列中该指标的值，来评估其作为因变量的有效性。
我们将Box-Jenkins方法应用于50个疫情前的出生队列（即2016年12月至2020年1月），并使用所得的传递函数来预测我们建议的选择指标在2020年2月开始的10个后续出生队列中的反事实值。然后，我们绘制所有60个残差值及其95%的检测区间。如果疫情开始时处于妊娠期的出生队列中生长缓慢的胎儿丢失数量超过历史预期，那么最后10个（即受疫情影响的）残差中就会有不止一个低于检测区间。
我们的男性和女性指标的最后10个残差中有4个低于95%的检测区间。
与选择理论一致，在新冠疫情开始时处于妊娠期的瑞典出生队列中，生长缓慢的婴儿数量少于预期。
