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Which childhood activities predict healthy adulthood?

December 8th, 2011

Encouraging kids to be more active is one of those motherhood-and-apple-pie goals that pretty much everyone sees as an excellent idea. Still, it’s worth asking: do the kids who are most active grow up to be the adults who are most active? And perhaps more importantly, which types of childhood activity (school phys ed? sports? unstructured play? walking or biking to school?) are most effective at establishing lifelong habits of physical activity?

Researchers in Australia just published a big study on the British Journal of Sports Medicine that followed up on 2,201 kids who had completed a detailed physical activity questionnaire way back in 1985, when they were between the ages of 9 and 15. The goal was to figure out whether and how “frequency and duration of discretionary sport and exercise (leisure activity), transport activity, school sport and physical education (PE) in the past week and number of sports played in the past year” when they were kids influenced their activity patterns as adults between the ages of 26 and 36.

Depending on how you look at it, the results are either very simple or very complicated. You can delve into all the nitty-gritty details of which childhood factors seem linked to which adulthood factors — and find puzzling and seemingly contradictory trends like this:

Higher levels of school sport among older males were associated with a 40% increase in the likelihood of being in the top third of total weekly activity in adulthood, but with a 40% lower likelihood among younger males.

Does this mean that school sport is bad for 9- to 12-year-olds and good for 13- to 15-year-olds? Probably not. As discussed earlier this week, when you search for links between large numbers of variables in a big collection of data, you’ll always find some relationships that appear statistically significant but in fact have little or no meaning. When you look at this data as a whole, there are a few “significant” associations, but there’s no overall trend, as the researchers acknowledge:

[F]ew associations were evident, most were relatively weak in magnitude and, for some activities, inconsistent in direction.

In other words, if you take a group of 12-year-olds and look at how active they are, you’ll have very little ability to predict which of those kids will have healthy, active lifestyles 20 years later. This is a bit of a bummer, because it makes it harder to decide exactly what types of physical activity are most useful for forming lifelong activity patterns. But don’t make the mistake of thinking that this implies that school phys ed (and other childhood physical activity) isn’t useful! Phys ed for 12-year-olds may not produce healthy 30-year-olds, but it sure as heck produces healthy 12-year-olds — and that’s a worthwhile goal on its own.

And hey, there’s also the fact that (as Gretchen Reynolds wrote about in the New York Times last week), a little bit of physical activity makes you perform better on tests. What kid wouldn’t want a boost of brain-derived neurotrophic factor coursing through his veins and boosting his memory as he heads back to math class?

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  1. Audrey Giles
    December 8th, 2011 at 22:26 | #1

    Hang on – what about the girls? Easy on your generalizations about “kids,” Alex, when the data reported are only about males.

  2. alex
    December 8th, 2011 at 23:19 | #2

    @Audrey: Oops, misleading phrasing by me: the subjects were both boys and girls, roughly equally represented. The random example of a correlation that I provided was for boys; girls had different correlations, but equally scattered (i.e. suggestive that there was no overall effect).

    And of course, my last sentence uses “his” and “he” when it should use “his or her” and “he or she.” Funnily enough, I paused in writing it, wondering whether to use the awkward “his or her,” the grammatically incorrect “their,” or the sexist “his.” I opted for the last one, but should have stuck to the first option! Thanks for bringing it up, and my apologies for the sloppiness.

  3. Audrey Giles
    December 9th, 2011 at 14:25 | #3

    Thanks for the explanation. (PS: the incorrect use of “their” instead of his/her a huge pet peeve of mine…as my grad class knows all too well!).

  4. Phil Koop
    December 9th, 2011 at 15:21 | #4

    Yes, it’s a bummer if you are responsible for devising exercise programs. On the other hand, at least it suggests that exercise behaviour is plastic; the results are not consistent with Taubes’ “exercise drive” theory.

  5. alex
    December 9th, 2011 at 15:45 | #5

    Good point, Phil — I could have reported this as a good news story: Adults are not doomed to sloth just because they hated sports when they were kids! In all seriousness, that IS an encouraging message. (And of course, the “exercise drive” idea is simply bunk.)

  6. Bman
    December 10th, 2011 at 04:34 | #6

    @alex – could have used “one” instead of “he.”

    I wonder about the very generic “played sports.” This can mean a lot of different things. Serious athletes may have a different outcome than others (for either outcome). For instance, at least for endurance athletes (and I’m sure for sprinters as well) what one does in one’s school years appears to play a major role on one’s epigenetics, making one more capable when older and possibly more likely to be active. However, there is also the case of burnout seen far too often among those who were serious athletes as kids, which could make one less likely to be active as an adult.

  7. Bman
    December 10th, 2011 at 04:41 | #7

    Just to add to my previous post:

    I suspect this issue is a lot like the risk factors for obesity. One of the biggest risk factors for obesity is who you associate with. Hang out with obese people and you are far more likely to be or become obese. Hang out with those who exercise, you are far more likely to exercise. Hang out with those who don’t, and you are far less likely to exercise. I’m guessing that and some other social issues are the biggest factors by so much that what phys ed classes you had as a kid or what sports teams your parents enrolled you in as a kid just becomes noise in the data.

    20 years is a long time, and those are rather important 20 years in development, so it probably shouldn’t be surprised that factors form 20 years earlier are dampened out.

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