Table 1.

Geometric Means of Urinary Creatinine (Milligram per Deciliter) and Specific Gravity (SG) Among All Participants and Tobacco Users* in NHANES 2007–2008

	Nonsmoker geometric mean (95% CI)			Smoker geometric mean (95% CI)
	N †	Creatinine	SG	N †	Creatinine	SG
All	4,993	95.11 (91.40–98.97)	1.017 (1.017–1.018)	1,391	104.34 (97.10–112.13)	1.017 (1.016–1.018)
Male	2,365	115.65 (111.84–119.58)	1.019 (1.019–1.019)	853	118.29 (107.55–130.10)	1.018 (1.017–1.019)
Female	2,628	80.36 (76.6484.26)	1.016 (1.015–1.016)	538	85.85 (80.00–94.50)	1.016 (1.014–1.017)
NHW	1,884	90.78 (85.86–95.98)	1.017 (1.016–1.017)	707	96.52 (89.23–104.41)	1.016 (1.016–1.017)
NHB	1,041	127.19 (121.37–133.29)	1.019 (1.019–1.020)	355	143.44 (134.04–153.51)	1.019 (1.018–1.020)
MA	1,192	98.70 (92.13–105.73)	1.019 (1.018–1.019)	148	110.51 (91.62–133.29)	1.018 (1.016–1.021)
OTH race	876	90.53 (84.49–96.99)	1.017 (1.017–1.018)	181	114.53 (90.87–144.36)	1.019 (1.017–1.021)
Ages 6–11 years	858	77.88 (73.01–82.88)	1.019 (1.019–1.020)	4	73.14 (N/A)	1.02 (N/A)
Ages 12–19 years	825	126 (118–135)	1.021 (1.019–1.021)	120	146.55 (122.75–174.97)	1.021 (1.019–1.023)
Ages 20–44 years	1,262	106 (102–111)	1.018 (1.017–1.018)	630	118.49 (109.49–128.24)	1.018 (1.017–1.019)
Ages 45–64 years	1,131	88 (82–94)	1.017 (1.016–1.017)	477	86.04 (76.87–96.31)	1.015 (1.014–1.016)
Ages ≥65 years	917	76 (73–80)	1.015 (1.014–1.015)	160	77.374 (63.93–93.64)	1.015 (1.014–1.017)

*Tobacco users/smokers defined as having serum cotinine concentrations >10 ng/ml.

^† N = nonmissing and unweighed sample size (excluding unknown smoking status due to missing cotinine measurements).

Upper and lower 95% confidence intervals (CIs) are shown in parenthesis.