Figure 1.

Procedure for the study design. Participants in this study are from the population-based TwinGene project within the Swedish Twin Registry, including 12,614 Swedish twins (European ancestry) born between 1911 and 1958. Between 2004 and 2008, the participants’ height, weight, hip and waist circumference, as well as the BP were measured. Serum levels of fasting glucose and lipids were measured by routine methods on a semi-automated biochemistry analyzer. During 2010–2012, serum levels of creatinine and cystatin C were measured. Twin order was randomly assigned and the singletons were removed. Finally, 4721 complete twin pairs (1327 monozygotic, 1780 same-sex dizygotic, and 1614 opposite-sex dizygotic pairs) with both creatinine and cystatin C were used in this cross-sectional twin study. CKD-EPI, CKD Epidemiology Collaboration.