Parental Shift Works and Children's Cognitive Outcomes: A Sibling Fixed-Effects Regression Model

Background: With the rise of a 24/7 economy, a growing body of research has examined the impacts of parental shift works, which are especially prevalent among welfare leavers and low-income families, on child development, including cognitive outcomes. Given that parents with shift works may represent distinct groups, it is important to deal with selection bias and/or omitted variable bias in estimating the effects of parental shift works. However, previous empirical studies have often relied on observational data and conventional linear regression, which is unable to control for unmeasured parental characteristics (e.g., parental intelligence). Hence, it is unclear whether their findings reflect causal effects or biased results. In order to address this limitation, we examined the association between parental shift works and children’s cognitive outcomes (under age 5), using a sibling fixed-effects regression (SFE), which helps us make a better causal inference.

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.