EDTA blood samples were obtained at the time of enrollment into the WHS and stored in vapor phase liquid nitrogen (−170° C). Samples for lipoprotein particle analysis by proton NMR spectroscopy were thawed, aliquoted (200 ul), refrozen, and shipped on dry ice to LipoScience, Inc. (Raleigh, NC). Particle concentrations of lipoproteins of different sizes were calculated from the measured amplitudes of their spectroscopically distinct lipid methyl group NMR signals. Weighted-average lipoprotein particle sizes are derived from the sum of the diameter of each subclass multiplied by its relative mass percentage based on the amplitude of its methyl NMR signal.5 Particle diameters and coefficients of variation (CVs) are shown in Supplementary Table 1 . The NMR lipoprotein variables that we examined are those that are provided when ordering an NMR lipoprotein profile for clinical use.
In a laboratory (N. Rifai, Children's Hospital, Boston, MA) certified by the National Heart, Lung, and Blood Institute/Centers for Disease Control and Prevention Lipid Standardization program, baseline samples were thawed and analyzed for standard lipids and apolipoproteins. Standard lipids were directly measured using reagents from Roche Diagnostics (Indianapolis, IN), with CVs <3%. Apolipoproteins B100 and A-1 were measured using immunoturbidimetric assays (DiaSorin, Stillwater, Minn), with CVs of 5% and 3%, respectively.
In a laboratory (N. Rifai, Children's Hospital, Boston, MA) certified by the National Heart, Lung, and Blood Institute/Centers for Disease Control and Prevention Lipid Standardization program, baseline samples were thawed and analyzed for standard lipids and apolipoproteins. Standard lipids were directly measured using reagents from Roche Diagnostics (Indianapolis, IN), with CVs <3%. Apolipoproteins B100 and A-1 were measured using immunoturbidimetric assays (DiaSorin, Stillwater, Minn), with CVs of 5% and 3%, respectively.
