Author Contributions: Dr Bont had full access to all the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis. Study concept and design: Bont, Hak, Hoes, and Verheij. Acquisition of data: Bont and Verheij. Analysis and interpretation of data: Bont, Hak, Hoes, Macfarlane, and Verheij. Drafting of the manuscript: Bont, Hak, and Verheij. Critical revision of the manuscript for important intellectual content: Hoes, Macfarlane, and Verheij. Statistical analysis: Bont, Hak, and Hoes. Obtained funding: Hoes and Verheij. Administrative, technical, and material support: Bont, Verheij. Study supervision: Hak, Hoes, and Verheij.