Selection and the effect of prenatal smoking

Investigating change across time in prevalence or association: the challenges of cross-study comparative research and possible solutions

Cross-study research initiatives to understand change across time are an increasingly prominent component of social and health sciences, yet they present considerable practical, analytical and conceptual challenges. First, we discuss the key challenges to comparative research as a basis for detecting societal change, as well as possible solutions. We focus on studies which investigate changes across time in outcome occurrence or the magnitude and/or direction of associations. We discuss the use and importance of such research, study inclusion, sources of bias and mitigation, and interpretation. Second, we propose a structured framework (a checklist) that is intended to provide guidance for future authors and reviewers. Third, we outline a new open-access teaching resource that offers detailed instruction and reusable analytical syntax to guide newcomers on techniques for conducting comparative analysis and data visualisation (in both R and Stata formats).

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s44155-022-00021-1.

Secular changes in the association between advanced maternal age and the risk of low birth weight: A cross-cohort comparison in the UK

Existing studies provide contradictory evidence concerning the association between child health and advanced maternal age. A potential explanation for the lack of consensus on this issue is changes over time in the costs and benefits of giving birth at an advanced age. This is the first study to investigate secular changes in the characteristics of older mothers and in the association between advanced maternal age and child health. We use data from four UK cohort studies, covering births from 1958 to 2001, and use low birth weight (LBW) as a marker for child health. We find that across successive birth cohorts, the negative association between advanced maternal age and LBW becomes progressively weaker; and that this pattern is partially explained by secular changes in the characteristics of older mothers. Our results suggest that associations between maternal age and child outcomes are tied to a specific population and point in time.

Smoking and early retirement due to chronic disability

This paper considers the long-term effects of smoking on disability retirement in Sweden. Smoking is known to have damaging effects on health, but there is limited evidence on how the effects of smoking translate into worse labour market outcomes, such as the inability to work. In contrast to the few previous studies on smoking and disability retirement, we use a large population sample with registry information on smoking, which is recorded for all women who give birth in Sweden. Thanks to these comprehensive data, we are able to account for a much broader range of potential confounders. In particular, by the use of sibling and twin fixed effects, we account for unobserved heterogeneity in childhood environment and family characteristics. Given that smoking is often initiated in adolescence, one would suspect such factors to play important roles. Among individuals aged 50-64 in 2011, a simple model suggested smokers to have a 5 percentage point higher probability of receiving (full) disability pension, making them more than twice as likely as non-smokers to receive this. However, in a model with sibling fixed effects, the size of the effect was reduced by more than a third. The results point to the importance of confounders, such as childhood circumstances or behaviours, which were not accounted for by previous studies. We also consider effects on disability due to different health conditions. In relative terms, effects are the largest for circulatory conditions and tumours. Results are largely driven by health problems severe enough to merit hospitalization, and there is no evidence of a role played by financial incentives.

The impact of pre and perinatal lifestyle factors on child long term health and social outcomes: a systematic review

To understand the full extent of the impact of a trial, it is important to consider the long-term consequences of outcomes beyond the trial follow-up period, especially for early year's interventions. A systematic review of the literature associated with the long-term consequences of four key outcomes from the Building Blocks trial, specifically, low birth weight, smoking during pregnancy, interval to subsequent pregnancy and A&E attendance or inpatient admission was conducted. These factors were guided by the funders, the Department of Health, as being of particular interest in the UK context. Relevant studies were identified from a number of sources including large databases, reference checking and citation searching. The search yielded 3665 papers, 43 of which were considered appropriate for inclusion. Of these, 29 were relating to smoking during pregnancy, 13 to low birth weight, 0 to A&E attendances during early childhood and 1 to short (< 2 years) interval to subsequent pregnancy. Consistent associations were found between maternal smoking during pregnancy and the effects this has on children's health, educational attainment and likelihood of engaging in problem behaviour and criminal activity in later life. Low birth weight was also found to impact on children's long-term health and cognitive development. Subsequent pregnancies within two years of the previous birth were linked with increased likelihood of pre-term birth and neonatal death. Only minimal evidence was identified regarding the consequences of a short interval to second pregnancy and of child A&E and outpatient attendances. Given that these outcomes have been identified by the UK Department of Health as of particular interest for UK benefit, investment of research in these areas is recommended to establish a clearer picture of both short and long-term consequences.

Do Smoking Bans Improve Neonatal Health?

RESEARCH OBJECTIVE

To estimate the effects of smoking bans on neonatal health outcomes and maternal smoking behavior during pregnancy.

DATA SOURCES

Restricted-use 1991-2009 Natality Detail Files, a Clean Air Dates Table Report, and the Tax Burden of Tobacco.

STUDY DESIGN

A quasi-experimental study using difference-in-differences estimation based on legislative history of smoking restrictions or bans by type/place/county/state level. Dependent variables included average monthly percentage of healthy neonates, of term neonates born with low and very low birth weight, of premature births, of maternal smokers, and average number of cigarettes smoked daily during pregnancy. The analyses were restricted to singleton births and those that occurred in the same county as mother's county of residence.

DATA COLLECTION/EXTRACTION METHODS

The data from three data sources were combined using Federal Information Processing Standard codes.

PRINCIPAL FINDINGS

Results of the overall and stratified by maternal smoking status, educational level, and age regression analyses suggested no appreciable effect of smoking bans on neonatal health. Smoking bans had also no effect on maternal smoking behavior.

CONCLUSION

While there are health benefits to the general population from smoking bans, their effects on neonatal health outcomes and maternal smoking during pregnancy seem to be limited.

Cumulative inequality in child health and academic achievement

Our understanding of health and social stratification can be enriched by testing tenets of cumulative inequality theory that emphasize how the accumulation of inequality is dependent on the developmental stage being considered, the duration and stability of poor health, and the family resources available to children. I analyze longitudinal data from the British National Child Development Study (N = 9,252) to ask: (1) if child health is a source of cumulative inequality in academic achievement, (2) whether this relationship depends on the timing and duration of poor health, and (3) whether trajectories are sensitive to levels of family capital. The results suggest that the relationship between health and academic achievement emerges very early in life and persists and that whether we observe shrinking or widening inequality as children age depends on when we measure their health and whether children have access to compensatory resources.

Birth weight and family status revisited: evidence from Austrian register data

In this paper, we study the socio-economic determinants of birth weight, with a focus on the mother's family status. We use Austrian birth register data covering all births between 1984 and 2007 and find that a mother's marriage is associated with a higher birth weight of the newborn, in the range of 40 to 60 g. The significant impact is retained if we include mother fixed effects or use an instrumental variable approach to account for unobserved mother heterogeneity. However, the magnitude of the causal effect (37 g) clearly indicates the importance of selection into marriage. Divorce around pregnancy results in significantly lower birth weights than the birth weights of babies born to single mothers. Family status effects in the 2000s are stronger than they were in the 1980s, and quantile regressions suggest that family effects are more pronounced at the lower quantiles of the birth weight distribution and less pronounced at higher quantiles. We conclude that the life situation of expectant mothers has an important influence on the birth weight of newborns, especially at the lower tail of the birth weight distribution.