Table 6.

Univariate associations between pain with opening, TMJ sounds, and bruxofacets as etiologic risk factors measured categorically and incidence rate of first-onset TMD, OPPERA prospective cohort study, USA (2006–2011)

Putative risk factor	Category	N	Site-adjusted(1) TMD incidence rate (% of people per annum)	Study site-adjusted effect(2)	Site, demographic adjusted effect(3)	P-value	Imputed values for loss to follow-up(4)	P-value
Pain on unassisted opening	1 or more	959	4.13	1.43 (1.10, 1.84)	1.51 (1.16, 1.96)	0.002	1.56 (1.19, 2.04)	0.001
	0 [ref]	1703	2.87
Pain on assisted opening (un-terminated)	1 or more	677	3.81	1.28 (0.94, 1.73)	1.40 (1.03, 1.91)	0.031	1.47 (1.07, 2.00)	0.015
	0 [ref]	1387	2.96
Pain on assisted opening (terminated)	1 or more	469	4.50	1.66 (0.80, 3.42)	1.65 (0.80, 3.39)	0.170	1.58 (0.76, 3.26)	0.220
	0 [ref]	121	2.66
TMJ palpation sounds: right	1 or more	865	3.61	1.13 (0.86, 1.47)	1.13 (0.86, 1.47)	0.360	1.28 (0.96, 1.68)	0.083
	0 [ref]	1834	3.13
TMJ palpation sounds: left	1 or more	924	3.33	1.00 (0.76, 1.30)	0.99 (0.75, 1.29)	0.940	1.01 (0.75, 1.33)	0.950
	0 [ref]	1784	3.25
Number of locations with tooth wear (facets)	1 or more	2359	3.22	0.95 (0.66, 1.36)	0.97 (0.67, 1.39)	0.880	1.11 (0.75, 1.62)	0.600
	0 [ref]	338	3.34

⁽¹⁾Adjusted rates computed using Poisson regression controlling for study site (categorical variable, 4 levels). Estimated rate is for reference study site (University of Buffalo)

⁽²⁾Rate ratio represents relative increase in incidence rate of TMD relative to reference group. Calculated using Cox proportional hazard regression model adjusted for study site (categorical variable, 4 levels).

⁽³⁾As for footnote 2, with additional adjustment for age in years), gender (categorical, 2 levels), race/ethnicity (categorical, 2 levels) and lifetime U.S. residence (categorical, 2 levels)

⁽⁴⁾As for footnote 3, with inclusion of imputed TMD rates for subjects lost to follow-up and imputed data for values missing at baseline