Table 3.

The independent associations of serum cotinine level quartile (reference: ≤0.01 ng/ml) with frailty.

Model, frail vs. robust			OR (95% CI)	P-value
Independent variable	Serum cotinine level, ng/ml	Quartile 4 >0.04	2.349 (1.081, 5.107)	0.031
		Quartile 3 0.02 < cotinine ≤ 0.04	0.714 (0.265, 1.923)	0.506
		Quartile 2 0.01 < cotinine ≤ 0.02	0.790 (0.313, 1.996)	0.618
		Quartile 1 ≤0.01	Reference	-
Control variables	Age, years		1.087 (1.033, 1.144)	0.001
	Depressive symptoms		1.229 (1.151, 1.313)	<0.001
	Total cholesterol, mg/dL		0.994 (0.986, 1.002)	0.167
	Systolic blood pressure, mmHg		0.996 (0.978, 1.013)	0.622
	Sex	Male	0.248 (0.121, 0.508)	<0.001
		Female	Reference	-
	Race/ethnicity	Mexican Americans	1.107 (0.207, 5.924)	0.906
		Other Hispanics	0.553 (0.104, 2.931)	0.486
		Non-Hispanic Whites	0.942 (0.253, 3.502)	0.929
		Non-Hispanic Blacks	1.236 (0.301, 5.065)	0.769
		Other	Reference	-
	Education	Below high school	3.489 (1.553, 7.840)	0.002
		High school graduate	1.142 (0.523, 2.494)	0.739
		Some college or above	Reference	-
	Alcoholic drinks/day	0–1 drink	1.173 (0.428, 3.212)	0.756
		2 drinks	0.857 (0.281, 2.617)	0.787
		3 or more drinks	Reference	-

Bolded values mean statistical significance (P < 0.05).