The physical environment and physical activity: a critical appraisal of review articles

Background: Over the last few years an increasing number of studies investigating the association between the physical environment and physical activity have been published. Many reviews have also summarized this emerging body of research, and such review papers are frequently used by public health policymakers and researchers themselves to inform decision making. Methods: This paper systematically appraises methodologic aspects of literature reviews examining the relationship between physical activity and the physical environment published in peer-reviewed journals between 2000 and 2005. Eleven reviews and their antecedent source papers were examined. Results: The majority of these reviews omitted between one third and two thirds of the studies that could have been eligible for inclusion at the time they conducted the review. Methodologic information on how the review was conducted was not always provided. Furthermore, in some cases results of a study were reported incorrectly, or physical environmental aspects were conflated with social environmental or cognitive factors. Moreover, when results were reported incorrectly, physical environmental variables were almost always reported as significantly associated with physical activity, when these associations were nonsignificant, or were not assessed as part of the primary study. Conclusions: Users of reviews in this field should be aware that there are significant methodologic variations among them, and that some reviews may include only a sample of the relevant primary studies. However, this is difficult to determine given the frequent incompleteness of review method reporting. Greater standardization in the reporting of review methods may assist with future efforts to summarize studies of the relationship between physical environments and physical activity