Wednesday, March 26, 2014

Lazy kids blamed on lazy moms

I am a big believer in following scientific evidence, which is why I am especially critical of experts who do not. But there is remarkably little evidence that any childrearing strategies are any better than any others. Here is a widely reported story saying moms should get more exercise to set a good example for their kids:
Parents who are physically active are more likely to have children who are physically active, but a new Cambridge-led study is the first to indicate a direct link between the activity level of a mother and that of her child.

The study analyzed the physical activity levels of 554 mothers and pre-schoolers, using activity monitors that were attached to participants and worn continuously to ensure accurate data. The mothers and children were monitored all day for up to seven days.

Research found that how active the mother was each day was closely linked to the activity level of the child. Yet the activity level of the mothers overall was quite low, with only 53% of mothers performing at least 30 minutes of moderate-to-vigorous physical activity at least once a week.

The study shows that children aren't "just naturally active" and take cues from their parents in regards to physical activity and other measures that make up a healthy lifestyle.

"We saw a direct, positive association between physical activity in children and their mothers -- the more activity a mother did, the more active her child. Although it is not possible to tell from this study whether active children were making their mothers run around after them, it is likely that activity in one of the pair influences activity in the other," said study leader Kathryn Hesketh (formerly of Cambridge and now UCL).
Here is the actual study:
METHODS: In the UK Southampton Women’s Survey, physical activity levels of 554 4-year-olds and their mothers were measured concurrently by using accelerometry for ≤7 days. ...

CONCLUSIONS: Physical activity levels in mothers and their 4-year-old children are directly associated, with associations at different activity intensities influenced by temporal and demographic factors. Influences on maternal physical activity levels also differ by activity intensity. Providing targeted interventions for mothers of young children may increase both groups’ activity.
This is just a correlation, so they cannot tell whether the moms are influencing the kids or the kids are influencing the moms. Or maybe the moms and kids are both mimicking the dads.

The more obvious explanation is that it is all in the genes. Many, and possibly all, human behaviors are heritable. That is, the genetic parents' behaviors are correlated with the kids' behaviors, even if the kids are adopted out and never meet their parents.

These research papers are cited cited as evidence-based advice for parents, with this one saying that moms should be more active in order to encourage more active kids. But the study does not show that at all. They could have randomly asked half the moms to increase their activity level, and then tested for an increase in the kids, but they did not do that.

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