DCD
Developmental coordination disorderDevelopmental coordination disorder (DCD) is a common, neurodevelopmental disorder of children that results in significant impairment in everyday activities of living. Over the past two decades, a large body of work has documented associations between DCD, physical inactivity, and poor health-related fitness. The exact nature of these relations, however, has been relatively little studied. In this paper, we ask whether the balance of evidence supports the proposition that DCD is a fundamental cause of inactivity and poor fitness. To address this question, we apply Hill's criteria for causation. We conclude that the evidence is consistent with, and reasonably supportive of, this proposition, but does not exclude alternative explanations.Developmental coordination disorder (DCD) is a neurodevelopmental disorder affecting motor coordination with a reported prevalence of between 1.8 and 5% of school-aged children.
1-3Both fine and gross motor control are affected, and resulting functional limitations lead to difficulties in many activities of daily living. In recent years, much attention has focused on the impact of DCD on physical activity. On average, children with DCD are less physically active than others, 4 reporting lower levels of participation both in free and in organized active play.5 It has been argued that, as a result, these children are at increased risk for obesity 6 and poor health-related fitness in general, 7 with potentially serious health consequences later in life.The past decade, in particular, has seen the accretion of a large body of literature on these associations. 8,9 There is some evidence that inactivity is a cause of poor motor functioning, and some that poor motor functioning is a cause of inactivity. In one popular model, this relation is characterized as a negative feedback loop: poor motor functioning leads to decreased activity, which leads to a failure to develop motor skills and to poor fitness, both of which may further discourage physical activity. 8 Although this model recognizes that motor functioning and inactivity are reciprocally related, most of its proponents would argue that poor motor coordination is the root cause-the spark that initiates the cycle. This belief, however, has gone largely untested.In this paper, we ask what recent work suggests about the direction of causality in these otherwise well-studied relations. We do not do this with the aim of firmly identifying a chain of cause and effect, but with the more modest one of deciding whether the weight of evidence suggests that one view or another is likelier. To do so, we use a well-known framework in epidemiology: the Bradford Hill criteria.