Health Outcomes of Only Children across the Life Course: An Investigation Using Swedish Register Data

Katherine Keenan , University of St Andrews
Kieron Barclay, Stockholm University
Alice Goisis, University College London

The proportion of only children – children with no full biological siblings – is growing in high-income settings, but we know little about their life course outcomes and how this is related to long-term health. Previous studies of only children have tended to focus on short-term, developmental and intellectual outcomes of only children in early life or adolescence, and provide mixed evidence. Using Swedish population register data on children born between 1940 and 1975, we compare only children with children of different sibship types, taking into account birth order, family size and half-siblings, to account for increased family complexity. We consider physical health outcomes measured at late adolescence (height, body mass index and fitness scores), and mortality. Only children with and without half-siblings had lower height and fitness scores, were more likely to be overweight or obese, and had higher mortality, than those with 1 or 2 biological siblings. Only children without half-siblings generally did better than only children with half-siblings, suggesting additional disadvantage accruing to only children experiencing parental disruption. With the exception of height, the results held after adjustment for parental characteristics and after employing within-family cousin comparison designs. In mortality models, some of the excess risk for only children was explained by adjustment for fertility, marriage and educational history. There is a need for further evidence on family size and life course outcomes across settings with different levels of social and health selectivity of only children.

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 Presented in Session 85. Early Life Conditions and Health