Validity of Waist-to-height Ratio as a Screening Tool for Type 2 Diabetes Risk in Non-Hispanic Whites, Non-Hispanic Blacks, and Mexican American Adult Women

Abstract Validity of waist-to-height ratio as a screening tool for type 2 diabetes risk in non-Hispanic Whites, non-Hispanic Blacks, and Mexican American Adult Women, from the ages 20-65 years of age. Background: A prominent screening measure for type 2 diabetes is a simple measure of waist circumference. Waist circumference is an aggregate measurement of the actual amount of total and abdominal fat accumulation and is a crucial correlate of the complexities found among obese and overweight patients. However, waist circumference does not take into consideration the frame of an individual. Hence, recent epidemiologic data have suggested the use of height adjusted waist circumference (waist-to-height ratio). The use of waist-to-height ratio in screening for type 2 diabetes is poorly understood. Aims: The aim of this study is to determine racial/ethnic differences in the association of the independent variables waist-to-height ratio and waist circumference, with type 2 diabetes in non-Hispanic Whites, non-Hispanic Blacks, and Mexican American adult women, ages 20-65 years old. Methods: Data from the NHANES 2007-2008 surveys were used. Race/ethnic specific odds ratios from univariate and multivariate logistic regression models were to estimate the associations of waist-to-height ratio and waist circumference with type 2 diabetes. In the multivariate models, adjustments were made for age and alcohol use. Results: In the univariate models, WC was associated with 1.06, 1.07 and 1.04 increased odds of type 2 diabetes in Mexican Americans, non-Hispanic Whites and non-Hispanic Blacks, respectively. The corresponding values waist-to-height ratio were 2.85, 3.20 and 1.88, respectively. On adjusting for confounders, WC was associated with 1.07, 1.05, and 1.05 increased odds of type 2 diabetes in Mexican Americans, non-Hispanic Whites and non-Hispanic Blacks, respectively. WHtR was associated with 2.95, 2.38, and 2.37 increased odds of type 2 diabetes in Mexican Americans, non-Hispanic Whites and non-Hispanic Blacks, respectively. Conclusion: This study indicates that WHtR may be a powerful anthropometric predictor of risk for type 2 diabetes for Mexican American, non-Hispanic White and non-Hispanic Black American women ages 20-65.The literature on WHtR as a screening tool for type 2 diabetes in American women is lacking. This study is one of the first to examine the association between WHtR across varying races of American women. Future researchers should explore populations of women and men in the US with more races represented

Using public control genotype data to increase power and decrease cost of case–control genetic association studies

Genome-wide association (GWA) studies are a powerful approach for identifying novel genetic risk factors associated with human disease. A GWA study typically requires the inclusion of thousands of samples to have sufficient statistical power to detect single nucleotide polymorphisms (SNPs) that are associated with only modest increases in risk of disease given the heavy burden of a multiple test correction that is necessary to maintain valid statistical tests. Low statistical power and the high financial cost of performing a GWA study remains prohibitive for many scientific investigators anxious to perform such a study using their own samples. A number of remedies have been suggested to increase statistical power and decrease cost, including the utilization of free publicly available genotype data and multi-stage genotyping designs. Herein, we compare the statistical power and relative costs of alternative association study designs that use cases and screened controls to study designs that are based only on, or additionally include, free public control genotype data. We describe a novel replication-based two-stage study design, which uses free public control genotype data in the first stage and follow-up genotype data on case-matched controls in the second stage, that preserves many of the advantages inherent when using only an epidemiologically matched set of controls. Specifically, we show that our proposed two-stage design can substantially increase statistical power and decrease cost of performing a GWA study while controlling the type I error rate that can be inflated when using public controls due to differences in ancestry and batch genotype effects