TABLE 2

Multiple logistic regression analysis of measures of β-cell function and 5-year risk of type 2 diabetes in IRAS, adjusted for age, sex, ethnicity, and clinic

Independent variable	Stratification variable	Adjusted for age, sex, ethnicity, and clinic			Interaction term
Independent variable	Stratification variable	OR*	95% CI	χ²	P value
AIR
	Ethnicity
	NHW	0.25	0.12–0.53	13.1†	0.45
	Black	0.42	0.20–0.74	8.9‡
	Hispanic	0.39	0.24–0.64	13.6†
	OGTT
	NGT	0.55	0.34–0.89	6.0§	0.31
	IGT	0.40	0.25–0.64	14.4‖
	Waist
	<Median	0.28	0.14–0.55	13.6†	0.46
	≥Median	0.34	0.23–0.50	28.4‖
	S₁
	<Median	0.41	0.29–0.57	27.2‖	0.01
	≥Median	0.12	0.04–0.37	13.3†
Intact PI
	Ethnicity
	NHW	3.82	2.51–5.84	38.7‖	0.002
	Black	1.38	1.02–1.86	4.3§
	Hispanic	1.60	1.22–2.10	11.4‡
	OGTT
	NGT	2.21	1.63–3.02	25.6‖	0.014
	IGT	1.35	1.07–1.69	6.7‡
	Waist
	<Median	2.43	1.45–4.07	11.3†	0.35
	≥Median	1.62	1.32–2.00	20.5‖
	S₁
	<Median	1.48	1.22–1.78	15.3‖	0.49
	≥Median	2.68	1.53–4.70	12.0†
Split PI
	Ethnicity
	NHW	3.06	2.12–4.42	35.6‖	0.07
	Black	1.38	1.05–1.81	5.5‡
	Hispanic	1.94	1.42–2.65	17.2‖
	OGTT
	NGT	1.90	1.48–2.44	25.2‖	0.33
	IGT	1.55	1.21–1.98	12.1‡
	Waist
	<Median	1.91	1.23–2.97	8.2‡	0.81
	≥Median	1.76	1.44–2.15	30.2‖
	S₁
	<Median	1.61	1.34–1.94	25.1‖	0.96
	≥Median	2.10	1.11–3.97	5.2§

Insulin
	Ethnicity
	NHW	2.80	1.79–4.38	20.5‖	0.28
	Black	1.13	0.83–1.53	0.6
	Hispanic	1.75	1.23–2.45	10.6‡
	OGTT
	NGT	1.86	1.32–2.64	12.3‡	0.12
	IGT	1.26	0.99–1.59	3.6
	Waist
	<Median	1.39	0.90–2.16	2.2	0.79
	≥Median	1.49	1.14–1.93	8.8‡
	S₁
	<Median	1.66	1.25–2.21	12.3†	0.02
	≥Median	0.95	0.59–1.52	0.6

Analyses were stratified by potential effect-modifying variables, including ethnicity, baseline IGT, baseline abdominal adiposity, and baseline insulin resistance.
*
* ORs refer to risk associated with a 1 SD increase in the independent variable.
†
† P < 0.001;
‡
‡ P < 0.01;
§
§ P < 0.05;
‖
‖ P < 0.0001. Definition of strata of potential effect modifiers: ethnicity (non-Hispanic white [NHW], black, Hispanic [His]), IGT (no/yes), abdominal adiposity (less than versus equal to or greater than the sex-specific median for waist circumference [males = 94 cm, females = 85 cm]), and insulin resistance (less than versus equal to or greater than the median for S₁ [1.64 min · μU⁻¹ · ml⁻¹]).