Childhood Obesity and Device‐Measured Sedentary Behavior: An Instrumental Variable Analysis of 3,864 Mother–Offspring Pairs

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A new paper titled “Childhood Obesity and Device‐Measured Sedentary Behavior: An Instrumental Variable Analysis of 3,864 Mother–Offspring Pairs” was just published in the Obesity journal.  The full-text article is available here (open access). Citations details, a summary of the paper, and highlights are reposted below. 

Hamer, M., Chastin, S., Viner, R.M. and Stamatakis, E. (2021), Childhood Obesity and Device‐Measured Sedentary Behavior: An Instrumental Variable Analysis of 3,864 Mother–Offspring Pairs. Obesity, 29: 220-225. https://doi.org/10.1002/oby.23025

ABSTRACT

Objective

Intergenerational data on mother–offspring pairs were utilized in an instrumental variable analysis to examine the longitudinal association between BMI and sedentary behavior.

Methods

The sample included 3,864 mother–offspring pairs from the 1970 British Cohort Study. Height and weight were recorded in mothers (age 31 [5.4] years) and offspring (age 10 years) and repeated in offspring during adulthood. Offspring provided objective data on sedentary behavior (7‐day thigh‐worn activPAL) in adulthood at age 46 to 47 years.

Results

Maternal BMI, the instrumental variable, was associated with offspring BMI at age 10 (change per kg/m2, β = 0.11; 95% CI: 0.09 to 0.12), satisfying a key assumption of instrumental variable analyses. Offspring (change per kg/m2, β = 0.010; 95% CI: −0.02 to 0.03 h/d) and maternal BMI (β = 0.017; 95% CI: 0.001 to 0.03 h/d) was related to offspring sedentary time, suggestive of a causal impact of BMI on sedentary behavior (two‐stage least squares analysis, β = 0.18 [SE 0.08], P = 0.015). For moderate‐vigorous physical activity, there were associations with offspring BMI (β = −0.010; 95% CI: −0.017 to −0.004) and maternal BMI (β = −0.007; 95% CI: −0.010 to −0.003), with evidence for causality (two‐stage least squares analysis, β = −0.060 [SE 0.02], P = 0.001).

Conclusions

There is strong evidence for a causal pathway linking childhood obesity to greater sedentary behavior.

Study importance

What is already known?

  • The association between sedentary behavior and obesity remains unclear.
  • Methodological constraints make it difficult to shed light on causality and directionality.

What does this study add?

  • We used an instrumental variable (maternal BMI) to examine associations between obesity and sitting.
  • Our data support a causal pathway linking childhood obesity to greater sedentary behavior in adulthood.

How might the results change the direction of research or the focus of clinical practice?

  • Policies to promote physical activity should focus on preventing childhood obesity and weight gain.
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