Effectiveness of intervention on physical activity of children: systematic review and meta-analysis of controlled trials with objectively measured outcomes (EarlyBird 54)

Metcalfe et al.’s meta-analysis of physical activity interventions in children was a thought-provoking read. It is sobering to realise that we probably have a long way to go in this increasingly important area of health promotion.

However, I think it is important to emphasise exactly what this study concludes. That is: if you pool together all the published trials which measured accelerometer data, the net result is that these interventions have, so far, not been effective. This is very different to concluding that “physical activity interventions do not work in children”, and I would echo Richard Weiler’s point here of not getting carried away with the press releases and headlines.

What unites all the studies included in this meta-analysis is that all the studies included used accelerometer data as an outcome measure (not necessarily as the primary one). The interventions themselves varied widely. Several of the interventions demonstrated statistically significant improvements in physical activity levels (Roemmich 2004, Goldfield 2006, Hughes 2008, Weintraub 2008).

Because the interventions varied so widely, combining them in all in single meta-analysis is a dubious academic move, analogous to doing a combined meta-analysis on all antihypertensive medication trials, when the question we really want to answer is “which one works best?” If I had done a trial on whether providing all children with a TV in their bedroom and closing down all swimming pools improved physical activity levels, would this also have been included in this meta-analysis?

Improving physical activity levels in children should be a major public health objective, since low levels of activity in childhood correlate strongly with numerous adverse health outcomes in later life. We should be looking at these studies carefully, deciding which ones seemed to be effective, and why, and then designing larger scale trials to demonstrate the evidence properly. Meanwhile, it remains our moral duty as health care providers to emphasise the huge importance of regular physical activity for health.