Table 3. . Multivariable Cox proportional hazards model stratified by age group.

Variable	Class	<65 years		≥65 years
		HR (95% CI)	p-value	HR (95% CI)	p-value
Sex	Male	Reference	–	Reference	–
	Female	0.68 (0.65–0.71)	<0.0001	0.86 (0.82–0.90)	<0.0001
Race	Caucasian	Reference	–	Reference	–
	Other	1.02 (0.95–1.09)	0.6518	1.00 (0.93–1.08)	0.9990
Insurance Status	Private	Reference	–	Reference	–
	Medicaid/other government	1.66 (1.56–1.78)	<0.0001	1.33 (1.11–1.58)	0.0016
	Medicare	1.68 (1.55–1.81)	<0.0001	1.17 (1.10–1.25)	<0.0001
	Not Insured	1.50 (1.39–1.62)	<0.0001	1.26 (0.93–1.70)	0.1396
Positive nodes, n	One node	Reference	–	Reference	–
	Two–three nodes or positive aspiration	1.62 (1.55–1.71)	<0.0001	1.39 (1.32–1.47)	<0.0001
	Four or more nodes or positive nodes documented but number unspecified	2.97 (2.81–3.14)	<0.0001	2.32 (2.19–2.46)	<0.0001
Charlson–Deyo score	0	Reference	–	Reference	–
	1	1.27 (1.19–1.36)	<0.0001	1.19 (1.13–1.26)	<0.0001
	2 or 3	1.81 (1.59–2.07)	<0.0001	1.60 (1.46–1.76)	<0.0001
Immunotherapy	No	Reference	–	Reference	–
	Yes	0.76 (0.72–0.79)	<0.0001	0.65 (0.61–0.70)	<0.0001

HR: Hazard ratio.