Abstract
Intergenerational data on mother-offspring pairs were utilized in an instrumental variable analysis to examine the longitudinal association between BMI and sedentary behavior. 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. 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). There is strong evidence for a causal pathway linking childhood obesity to greater sedentary behavior.
Highlights
Popular media and scientific literature alike often portray sedentary behavior as a stand-alone risk factor contributing to the obesity epidemic
Contemporary data have, suggested that the association more strongly operates in the direction from obesity to sedentary behavior/moderate-vigorous intensity physical activity (MVPA) rather than inactivity causing obesity [4,5,6,7,8]
We examined the distribution of offspring lifestyle and health variables according to maternal BMI, and effect estimates are presented as odds ratio and 95% confidence interval (CI) for a unit change in maternal BMI
Summary
Popular media and scientific literature alike often portray sedentary behavior as a stand-alone risk factor contributing to the obesity epidemic. Evidence from observational study settings has often relied on cross-sectional designs and self-reported data on sedentary behavior [3]. These methodological constraints make it difficult to shed light on causality and understand the direction of the association. Existing studies have generally had short follow-up periods, and residual confounding remains a concern, factors such as dietary intake. These studies were conducted on adult populations but have not examined associations across the life course from childhood to adulthood. It is important to understand whether early-life obesity drives sedentary
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