Table 2.

Percent reduction (95% CI) in urine cadmium geometric means comparing 1999–2008 and 1988–1994 in models with progressive degrees of adjustment.

Model adjustments	Overall (n = 19,759)	Never smokers (n = 10,107)	Ever smokers (n = 9,652)
Age		31.3 (26.9, 35.5)		24.9 (18.9, 30.5)		31.4 (27.1, 35.5)
Age, sex, race, education, and BMI		29.5 (25.1, 33.6)		23.7 (18.2, 28.8)		29.8 (25.3, 34.0)
Age, sex, race, education, BMI, and smoking status		27.2 (22.9, 31.2)		NA		30.5 (26.2, 34.5)b
Age, sex, race, education, BMI, smoking status, pack-year, and cotinine		21.7 (17.4, 25.9)		20.0 (14.1, 25.6)c		24.7 (20.4, 28.8)b
NA, not applicable. aThe change in the percent reduction in geometric means comparing urine cadmium concentrations in NHANES 1999–2008 with those in NHANES 1988–1994 after introducing a given variable (or set of variables) is interpreted as the amount of the reduction in urinary cadmium that can be attributed to that variable (or set of variables). For instance, for the overall population, the age-adjusted percent reduction of geometric mean of urine cadmium in NHANES 1999–2008 compared with 1988–1994 was 31.3%. After further adjustment for age, sex, race, education, and BMI, the percent reduction was 29.5%; that is, changes in those variables explained 5.7% of the age-adjusted percent reduction [1 – (29.5/31.3) × 100 = 5.7%]. bSmoking status in ever smokers only included former and current smokers. cAdjusted for serum cotinine only in analysis restricted to never smokers.