Table 4. Adjusted odds ratios for associations between the urine specific gravity and the risk of kidney stone in NHANES 2007–2008^a.

Characteristic	N	Basic model			Core model			Extended model
		aOR (95% CI)	P value		aOR (95% CI)	P value		aOR (95% CI)	P value
Urine specific gravity (g/mL)			0.004			0.008			0.008
<1.008	506	1.00			1.00			1.00
1.008–1.020	2,710	1.39 (0.96–2.01)	0.085		1.34 (0.93–1.95)	0.121		1.31 (0.90–1.91)	0.155
>1.020	1,575	1.81 (1.22–2.68)	0.003		1.74 (1.17–2.58)	0.006		1.71 (1.16–2.54)	0.007

^a, adjusted covariates: basic model: age, gender, race, education levels, and marital status; Core model: basic model plus diabetes, hypertension, and BMI; Extended model: core model plus estimated glomerular filtration rate (eGFR). CI, confidence interval; aOR, adjusted odds ratio.