Table 4.

Analysis of effects in parametric time-to-event models (full model and final model), in which the dependent variable is age at first use of assistive device for ambulation.

Independent variable	Regression coefficient	95% confidence interval	p-value
Full model
Hip flexion strengtha
MRC ≥4	12.60	7.41, 17.78	0.008
MRC ≤3	Ref	Ref
Gender
Female	−0.71	−5.50, 4.09	0.773
Male	Ref	Ref
Ethnicity
Not Hispanic	−1.63	−8.56, 5.29	0.644
Hispanic	Ref	Ref
Age at earliest symptom, yb	0.36	0.04, 0.68	0.027
BMI, kg/m2	−0.34	−0.96, 0.29	0.290
Blepharoptosis surgery
Yes	8.28	3.35, 13.20	0.001
No	Ref	Ref
Dysphagia treatment
Yes	−0.15	−4.87, 4.58	0.952
No	Ref	Ref
Gastrostomy
Yes	7.77	−2.51, 18.04	0.139
No	Ref	Ref
FCIc	−3.35	−7.22, 0.51	0.089
Final model
Hip flexion strength
MRC ≥4	12.27	6.81, 17.73	<0.0001
MRC ≤3	Ref	Ref
Age at earliest symptom, y	0.55	0.28, 0.82	<0.0001
Blepharoptosis surgery
Yes	7.28	1.70, 12.85	0.011
No	Ref	Ref

Abbreviations: Ref = reference; BMI = body mass index; FCI = Functional Comorbidity Index

^aFor categorical independent variables (hip flexion strength, gender, ethnicity, blepharoptosis surgery, dysphagia treatment, and gastrostomy), the regression coefficient for one value of the variable is used as the reference. The regression coefficient for the other value of the variable is interpreted as the number of years that first use of assistive device is delayed (for positive regression coefficients) or earlier (for negative regression coefficients) relative to the reference.

^bFor continuous independent variables (age at earliest symptom, BMI, and FCI), the regression coefficient is interpreted as the number of years that first use of assistive device is delayed (for positive regression coefficients) or earlier (for negative regression coefficients), for each unit increase in the independent variable.

^cFCI scores were positively skewed; therefore, a square root transformation was used in the regression model.