Improving current practice in reviews of the built environment and physical activity.

Over the last decade, there has been a marked increase in studies about built environments and physical activity. As the number of publications is growing rapidly, literature reviews play an important role in identifying primary studies and in synthesizing their findings. However, many of the reviews of effectiveness in this field demonstrate methodological limitations that might lead to inaccurate portrayals of the evidence. Some literature reviews a priori excluded intervention studies even though they provide the strongest level of evidence. The label 'systematic review' has mostly been used inappropriately. One of the major criteria of a systematic review that is hardly ever met is that the quality of the primary studies needs to be assessed and this should be reflected in the synthesis, presentation and interpretation of results. With few exceptions, 'systematic' reviews about environments and physical activity did not refer to or follow the QUORUM or PRISMA statements. This commentary points out the usefulness of the PRISMA statement to standardize the reporting of methodology of reviews and provides additional guidance to limit sources of bias in them. The findings and recommendations from this article can help in moving forward the synthesis of evidence of effectiveness not only in built environments and physical activity, but also more broadly in exercise science and public health.