Table 3.

Hazard ratios from the multivariate analysis of the CAL + BOP model given in Fig. 1. The likelihood ratio test was used to select this model. The risk for gingivitis onset was 51% higher in males than females while each year increase in age was associated with a 3% decrease in the risk of gingivitis onset.

	Hazard ratios and 95 % CI
Covariates	Health → Gingivitis	Health → Chronic periodontitis	Gingivitis → Health	Gingivitis → Chronic periodontitis
Gingival redness	2.15 (1.56, 2.98)*	0.48 (0.14, 1.70)	0.96 (0.64, 1.45)	3.11 (0.53, 18.34)
Smoking	0.72 (0.53, 1.00)	2.11 (1.19, 3.76)*	0.71 (0.48, 1.05)	1.02 (0.26, 3.97)
Gender: males	1.51 (1.10, 2.08)*	1.18 (0.67, 2.08)	1.22 (0.81, 1.84)	3.10 (0.84, 11.40)
Age	0.97 (0.96, 0.99)*	1.00 (0.97, 1.03)	0.98 (0.97, 1.00)	0.94 (0.87, 1.00)
Severity†	1.00 (0.97, 1.02)	1.07 (1.02, 1.12)*	1.00 (0.97, 1.04)	1.15 (1.06, 1.26)*

^†We estimated the severity of the disease in a subject at baseline by counting the number of teeth with CAL > 4 mm

^*Significant results at α = 0.05