Author Contributions: Drs Steingrimsdottir, Indridason, and Sigurdsson had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Indridason, Franzson, Sigurdsson.
Acquisition of data: Steingrimsdottir, Gunnarsson, Franzson.
Analysis and interpretation of data: Steingrimsdottir, Gunnarsson, Indridason, Franzson, Sigurdsson.
Drafting of the manuscript: Steingrimsdottir.
Critical revision of the manuscript for important intellectual content: Steingrimsdottir, Gunnarsson, Indridason, Franzson, Sigurdsson.
Statistical analysis: Gunnarsson, Indridason.
Obtained funding: Franzson, Sigurdsson.
Administrative, technical, or material support: Steingrimsdottir, Franzson, Sigurdsson.
Study supervision: Steingrimsdottir, Indridason, Franzson, Sigurdsson.
Financial Disclosures: None reported.
Funding/Support: This study was supported by a grant from the Science Fund of St. Josephs Hospital, Landakoti, and the University Hospital, Reykjavik, Iceland.
Role of the Sponsors: The funding sources did not participate in the design and conduct of the study, in the collection, analysis, and interpretation of the data, or in the preparation, review, or approval of the manuscript.
Acknowledgment: We thank the dedicated and talented staff of Clinical Chemistry, Landspitali-University Hospital, Reykjavik, Iceland. We are indebted to all the participants of this population-based study.