Table 3.

Cox model analysis of potential explanatory variables for risk of dystonia spread

Contrast	HR	95% CI	P value
Onset site
BSP versus cervical	10.980	6.459 to 18.667	<0.001*
BSP versus hand	5.154	2.338 to 11.361	<0.001*
BSP versus laryngeal	5.161	2.062 to 12.919	<0.001*
Cervical versus hand	0.469	0.207 to 1.063	0.089
Cervical versus laryngeal	0.470	0.182 to 1.213	0.143
Laryngeal versus hand	0.999	0.333 to 2.995	0.998
Sex (male versus female)	1.120	0.716 to 1.751	0.623
Age of onset (10 years)	1.091	0.898 to 1.325	0.378
Family history (yes versus no)	2.184	1.243 to 3.837	0.012*
Tremor dominant (yes versus no)	1.977	1.006 to 3.883	0.061
Sensory trick (yes versus no)	1.026	0.653 to 1.612	0.913
EtOH responsive (yes versus no)	2.590	1.316 to 5.097	0.009*

Results of the Cox proportional hazard model for time to first spread. Subjects without an observed spread were censored at the last observed dystonia duration time. Three observations were omitted because of missing covariates or time or censoring information. HRs greater than 1 indicate increased chance of dystonia spread, while HRs less than 1 indicate decreased chance. Testing of the proportional hazard assumption found no definite evidence of deviation from the assumption.

*Significant at p<0.05.

BSP, blepharospasm; EtOH, ethyl alcohol.