Age at quitting smoking as a predictor of risk of cardiovascular disease incidence independent of smoking status, time since quitting and pack-years

Table 5 Risk equation with age at quitting incorporated into smoking status variable (Model 2)

Variable	Parameter Estimate	Standard Error	Chi-Square	P value	Hazard Ratio	95% CI
Sex	0.5967	0.1133	27.7286	<.0001	1.816	1.454	2.268
Age	0.0730	0.0070	107.9667	<.0001	1.076	1.061	1.091
Sbp	0.0140	0.0036	14.7801	0.0001	1.014	1.007	1.021
Dbp	-0.0172	0.0069	6.1574	0.0131	0.983	0.970	0.996
Total/HDL ratio	0.2148	0.0354	36.7663	<.0001	1.240	1.157	1.329
Diabetes	0.7941	0.1520	27.2897	<.0001	2.213	1.642	2.981
Trglycerides	-0.0016	0.0005	8.2076	0.0042	0.998	0.997	0.999
Current smoker	0.7248	0.1505	23.1684	<.0001	2.064	1.537	2.773
Age at quitting
<37	0.0708	0.1474	0.2307	0.6310	1.073	0.804	1.433
> = 37	0.4578	0.1435	10.1778	0.0014	1.581	1.193	2.094
Test	Total	Event		Censored			% Censored
	3751	383		3368			89.79
	Chi-Square	DF				P value
Likelihood Ratio	448.6297	10				<.0001
Hosmer Lemeshow	11.3628	9				0.2516
Modified HL	10.5026	9				0.3113
	Estimate	SE				95% CI
C statistic	0.8085	0.0108				0.7873, 0.8296

Note: The reference categories for sex, diabetes and the smoking variable are female, no diabetes and never smoker respectively.

ISSN: 1756-0500