Table 2.

Association of intensity of cigarette smoking (heavy vs light and moderate smokers) and independent variables measured by the generalized additive model.

Estimation of parametric coefficients
Variable	Estimate (SE)	P-value	OR	95% CI
Marital status (married as reference)
Other	0.343 (0.237)	0.148	1.409	0.885–2.242
Level of education (illiterate as reference)
Lower than diploma	−0.069 (0.235)	0.767	0.932	0.589–1.479
Diploma and higher	−0.212 (0.272)	0.437	0.809	0.475–1.379
Residence (rural as reference)
Urban	−0.088 (0.149)	0.556	0.916	0.684–1.223
Employment status (employee as reference)
Worker	0.167 (0.287)	0.561	1.182	0.673–2.074
Self-employed	0.176 (0.242)	0.468	1.192	0.742–1.916
Retired	0.197 (0.307)	0.522	1.217	0.667–2.223
Unemployed	0.310 (0.322)	0.336	1.364	0.725–2.563
Other	0.178 (0.513)	0.728	1.195	0.437–3.266
Income level ($ 175 or less as reference)
More than $ 175	−0.298 (0.151)	0.048*	0.742	0.552–0.998
Try to quit (No as reference)
Yes	−0.463 (0.150)	0.002*	0.629	0.469–0.844
Expose to smoke at home (no as reference)
Yes	0.310 (0.131)	0.018*	1.364	1.055–1.763

Approximate significance of smooth terms (Non-parametric)
Smooth covariates	edf	Ref.df	Chi.sq	P-value
Age (year)	2.974	9	25.26	< 0.001*
Age at smoking onset (year)	1.913	9	41.41	< 0.001*

*Significant at 0.05.