Study population

The SHFS is a family-based longitudinal study designed to identify metabolic, genetic and behavioral factors for CVD, diabetes and their risk factors in American Indians in tribes and communities residing in Arizona, North/South Dakota, and Oklahoma. The SHFS recruited 3665 tribal members from 94 multigenerational families (14–93 years) between 2001 and 2003. All participants underwent a clinical examination including a personal interview and physical examination. Information on socio-demographic factors, medical history, medication use, and lifestyle factors was collected by personal interview using standard questionnaires. A physical examination was conducted, and fasting blood samples were collected for laboratory tests, including fasting glucose and lipids. The SHFS protocol was approved by the Institutional Reviews Boards from the Indian Health Service and the participating institutions. Study design and methods of the SHFS have been described elsewhere [29]. In the current study, 874 participants from one community were removed due to withdraw of consent. However, the subsample of 2791 participants did not differ significantly from the total sample of 3665 participants in the distribution of demographics. After excluding participants with overt CVD (n = 135) or missing LTL data (n = 88), a total of 2568 participants were included in the final data analysis.