“…Confounding covariates included age (continuous) [ 2 ], sex (male or female) [ 10 ], ethnicity (non-Hispanic white, non-Hispanic black, Mexican-American, or other) [ 11 ], obesity (underweight, normal, overweight, obese, or unknown) [ 3 , 12 ], education (< high school, high school, or > high school) [ 2 ], poverty-income ratio (< 130, 130–349%, ≥ 350%, or unknown) [ 10 , 13 ], and survey periods (1988–1991, 1991–1994, 1999–2000, 2001–2002, 2003–2004, 2005–2006, 2007–2008, 2009–2010, 2011–2012, or 2013–2014). NHANES III was conducted in two stages, i.e., from 1988 to 1991 and then from 1991 to 1994, and the subsequent cycles of NHANES were conducted once every 2 years.…”