Parental Shift Works and Children's Cognitive Outcomes: A Sibling Fixed-Effects Regression Model
Method: Using data from the National Longitudinal Survey of Youth 1979 (NLSY79) and its Child Supplement (NLSY-CS), we pooled 7838 children born to the NLSY female sample. Parental shift work was measured by five categories: 1) day shifts (if the main job begins at 6 am or later and ends by 6 pm); 2) evening shifts (between 2 pm and midnight); 3) night shifts (between 9 pm and 6 am); 4) other shifts (i.e., split-shift, rotating shift, and irregular hours); and 5) not working. Children’s cognitive outcome was measured by the Peabody Picture Vocabulary Test - Revised (PPVT-R). We conducted OLS regression followed by the SFE that regressed differences in sibling PPVT-R scores on differences in siblings’ exposure to parental shift work, differencing out any sibling-invariant characteristics associated with the family, including any unobserved heterogeneity that is constant across siblings within the family.
Results: Our OLS model suggested that paternal night shifts had a negative effect on children’s PPVT-R, while no maternal shift works had significant impacts. Specifically, the PPVT-R score of children with fathers working night shifts was on average about 7 points lower than that of their peers with fathers working standard day shifts (b=-7.36, p<.01), indicating that children with fathers working night shifts fell .35 standard deviation on the PPVT-R scale behind. However, in our SFE model, this negative effect of paternal night shifts dramatically decreased and was not statistically significant (b=-1.88, p>.05), indicating that there was essentially no difference in the PPVT-R between paternal night shifts and standard day shifts.
Implications: Unlike previous studies, our study does not provide empirical evidence that parental shift works have negative effects on children’s cognitive outcomes, suggesting that we should be cautious in making a causal claim from observational data. However, given that the SFE also has limitations, further research is needed to ascertain the causal nature of the intergenerational effects of parental shift works.