This paper searched for articles using MEDLINE and examined the reference lists of those articles identified. The search was restricted to English language publications in MEDLINE and so relevant studies could have been missed. No attempt was made to identify unpublished studies. The search could have been extended to other databases.
The authors provided details of the included studies in a comprehensive table. This listed the study design, patient characteristics, assessment of physical activity, odds ratios and 95% confidence intervals, and the factors adjusted for within the individual studies. The authors did not provide details of the methods used to select the articles for the review, or to judge their relevance and validity. However, they did assess the actions taken to avoid information bias, selection bias and the effects of confounding.
The results of the review should be viewed with caution since the primary studies were not assessed for quality, and were heterogeneous in their characteristics.