Shared unmeasured characteristics among siblings confound the association of Apgar score with stress resilience in adolescence

Abstract

AimWe investigated the association between low Apgar score, other perinatal characteristics and low stress resilience in adolescence. A within‐siblings analysis was used to tackle unmeasured shared familial confounding.MethodsWe used a national cohort of 527 763 males born in Sweden between 1973 and 1992 who undertook military conscription assessments at mean age of 18 years (17–20). Conscription examinations included a measure of stress resilience. Information on Apgar score and other perinatal characteristics was obtained through linkage with the Medical Birth Register. Analyses were conducted using ordinary least squares and fixed‐effects linear regression models adjusted for potential confounding factors.ResultsInfants with a prolonged low Apgar score at five minutes had an increased risk of low stress resilience in adolescence compared with those with highest scores at one minute, with an adjusted coefficient and 95% confidence interval of −0.26 (−0.39, −0.13). The associations were no longer statistically significant when using within‐siblings models. However, the associations with stress resilience and birthweight remained statistically significant in all analyses.ConclusionThe association with low Apgar score seems to be explained by confounding due to shared childhood circumstances among siblings from the same family, while low birthweight is independently associated with low stress resilience.

Higher body mass index at ages 16 to 20 years is associated with increased risk of a multiple sclerosis diagnosis in subsequent adulthood among men

“…This study used a register-based cohort described in greater detail elsewhere, 5 comprising males born between 1970 and 1992, included in the Swedish Military Conscription Register between ages 16 and 20 years. A total of 896,696 men were identified and 152,148 were excluded due to Swedish personal identification number errors (2166), conscription examination after age of 20 years (6747), an MS diagnosis before age of 20 years (32), death or emigration before age of 20 years (9,443), BMI ⩽ 15 (157), and missing information for age at conscription (58), socioeconomic characteristics (13,719), and height and weight (119,826).…”

Review of the Reliability and Validity of the Apgar Score

“…9 However, there is no clear definition how neonates with scores of 6 are clinically different from neonates with scores of 7. Further, researchers often arbitrarily create their own cut-off of normal/abnormal or score groupings to allow for statistical analysis, [48][49][50] which complicates comparisons of study outcomes and introduces bias.…”

Associations of parental and perinatal factors with subsequent risk of stress-related disorders: a nationwide cohort study with sibling comparison

“…It is not implausible that the observed association between preterm birth and stress-related disorders is explained by genetic factors that may influence both outcomes. It has been reported that low 5 min Apgar score is associated with less stress resilience in young adulthood [51]. Although the Apgar score can be seen as a proxy to many parental and perinatal conditions, the heritability is estimated to be 42% [52].…”