Table 2.

Association between baseline sex-specific SMI tertiles and incidence of metabolic syndrome (Cox model) (N = 14,830)

	Lowest tertile (n = 4943)	Middle tertile (n = 4944)			Highest tertile (n = 4943)			P for trend
	Referent	HR	95% CI	P value	HR	95% CI	P value
Model 1	1	0.56	0.52, 0.61	< 0.001	0.26	0.24, 0.29	< 0.001	< 0.001
Model 2	1	0.58	0.54, 0.63	< 0.001	0.28	0.25, 0.31	< 0.001	< 0.001
Model 3	1	0.91	0.83, 0.99	0.026	0.63	0.56, 0.70	< 0.001	< 0.001
Model 4	1	0.88	0.81, 0.97	0.006	0.60	0.54, 0.68	< 0.001	< 0.001
Subgroup analysesa
Sex						P for interaction = 0.923
Men (n = 8476)	1	0.91	0.82, 1.01	0.088	0.65	0.57, 0.75	< 0.001	< 0.001
Women (n = 6354)	1	0.87	0.73, 1.03	0.099	0.56	0.44, 0.70	< 0.001	< 0.001
Family history of diabetes						P for interaction = 0.954
Absence (n = 13,279)	1	0.91	0.83, 0.99	0.037	0.62	0.55, 0.70	< 0.001	< 0.001
Presence (n = 1551)	1	0.81	0.61, 1.08	0.144	0.47	0.31, 0.70	< 0.001	0.001
Smoking status						P for interaction = 0.314
Never (n = 8278)	1	0.86	0.75, 0.98	0.022	0.54	0.44, 0.65	< 0.001	< 0.001
Past (n = 4078)	1	0.85	0.73, 0.99	0.039	0.63	0.52, 0.78	< 0.001	< 0.001
Present (n = 2474)	1	0.95	0.80, 1.14	0.603	0.73	0.57, 0.92	0.009	0.023
Exercise						P for interaction = 0.325
Never (n = 12,593)	1	0.87	0.79, 0.96	0.005	0.62	0.54, 0.70	< 0.001	< 0.001
Regular (n = 2237)	1	0.99	0.79, 1.24	0.940	0.50	0.35, 0.70	< 0.001	< 0.001
Obesity						P for interaction < 0.001
Absence (n = 10,925)	1	0.77	0.68, 0.87	< 0.001	0.56	0.47, 0.66	< 0.001	< 0.001
Presence (n = 3905)	1	1.04	0.91, 1.18	0.568	0.97	0.85, 1.12	0.698	0.603
						P for interaction = 0.062
Age ≤ 50 (n = 8017)	1	0.92	0.81, 1.05	0.232	0.60	0.50, 0.72	< 0.001	< 0.001
Age > 50 (n = 6813)	1	0.83	0.74, 0.94	0.002	0.63	0.54, 0.73	< 0.001	< 0.001
IFG						P for interaction = 0.007
Absence (n = 13,129)	1	0.87	0.79, 0.96	0.006	0.59	0.51, 0.67	< 0.001	< 0.001
Presence (n = 1701)	1	0.91	0.74, 1.13	0.399	0.58	0.44, 0.77	< 0.001	< 0.001
						P for interaction = 0.019
HOMA-IRb ≤ 2.5 (n = 7957)	1	0.94	0.82, 1.07	0.344	0.71	0.59, 0.84	< 0.001	< 0.001
HOMA-IR > 2.5 (n = 2006)	1	1.14	0.95, 1.37	0.158	0.80	0.64, 1.00	0.053	0.002

Model 1: crude

Model 2: Model 1 + further adjusted for age

Model 3: Model 2 + further adjusted for BMI

Model 4: Model 3 + further adjusted for family history of diabetes, smoking status, regular exercise, eGFR, and CRP

BMI body mass index, CI confidence interval, CRP C-reactive protein, eGFR estimated glomerular filtration rate, HOMA-IR homeostasis model assessment of insulin resistance, HR hazard ratio, IFG impaired fasting glucose, SMI skeletal muscle mass index

^aSubgroup analyses were adjusted for Model 4

^bA total of 9963 subjects were analyzed due to missing HOMA-IR values