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. Author manuscript; available in PMC: 2023 Mar 1.
Published in final edited form as: Ann Epidemiol. 2022 Jan 3;67:73–80. doi: 10.1016/j.annepidem.2021.12.010

Table 1.

Ordinary least squares regression of the difference in siblings’ PALS-K scoresa (points) on their preterm birth statuses (N = 20,010 sibling pairs)

Unadjusted Regression
Coefficient (95% CI)		 Adjusted Regressionb
Coefficient (95% CI)
Preterm birth (gestational age <37 weeks)
Older sibling −2.49 (−3.83, −1.15) −2.28 (−3.62, −0.94)
Younger sibling 0.38 (−0.97, 1.73) 0.79 (−0.57, 2.14)
Spillover coefficientc −2.11 (−3.82, −0.40) −1.49 (−3.21, 0.22)
a

The difference in PALS-K scores equals the older sibling’s PALS-K Score minus the younger sibling’s PALS-K score.

b

Covariates include maternal age at delivery (years), maternal education at delivery (no high school diploma; high school diploma/equivalent; 1-3 years college; 4+ years college) and Medicaid delivery payment (no; yes), all of which were measured at the time of the older sibling’s delivery.

c

The spillover coefficient is the sum of the partial regression coefficients for the older sibling’s preterm birth indicator and the younger sibling’s preterm birth indicator. Assuming one-sided spillover as in Figure 1A, this identifies the effect of a younger sibling’s preterm birth on the older sibling’s PALS-K score.

Abbreviations: ”CI” confidence interval; ”PALS-K” Phonological Awareness Literacy Screening-Kindergarten.