Table 4.

Hazard ratios from the multivariate analysis of the PD + BOP model given in Fig. 2. Severity of disease at baseline was associated with an 11% increase in the hazard of chronic periodontitis onset from health state while each year increase in age was associated with 2% decrease in the hazard of gingivitis onset.

Hazard ratios (95 % CI)
Covariates	Health → Gingivitis	Health → Chronic periodontitis	Gingivitis → Health	Gingivitis → Chronic periodontitis
Gingival redness	2.13 (1.53, 2.97)*	3.43 (1.12, 10.52)*	1.13 (0.76, 1.68)	1.57 (0.38, 6.51)
Smoking	0.89 (0.66, 1.22)	2.20 (1.66, 7.37)*	1.02 (0.71, 1.45)	0.48 (0.05, 5.02)
Gender: males	1.39 (1.01, 1.91)*	0.77 (0.25, 2.39)	1.00 (0.68, 1.48)	7.43 (0.35, 15.63)
Age	0.98 (0.96, 0.99)*	1.00 (0.94, 1.06)	1.00 (0.98, 1.01)	0.88 (0.77, 1.02)
Severity†	0.96 (0.93, 1.00)	1.11 (1.00, 1.25)*	0.96 (0.92, 1.01)	1.12 (1.01 1.28)*

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

^*Significant results at a = 0.05