Table 3. Associations among patient characteristics and change in EQ-5D Index with linear regression.

Variable	Univariable		Multivariable
	Coefficient	p Value	Coefficient	95% CI	p Value
Age	−0.001	0.43
Female sex	0.005	0.90
BMI	−0.001	0.86
Smoking history	0.078	0.06	0.022	−0.056, 0.101	0.57
Diabetes	−0.036	0.53
Income (per $1,000)	−0.002	0.17	−0.001	−0.003, 0.002	0.46
Anxiolytic use	−0.113	0.04	−0.115	−0.208, −0.022	0.02
Antidepressant use	0.049	0.24
Narcotic use	−0.036	0.40
Multiple vertebral levels	−0.030	0.48
EQ-5D QALY score preoperative	−0.406	<0.0001	−0.532	−0.732, −0.332	<0.0001
PHQ-9 preoperative	0.007	0.01	−0.006	−0.014, 0.001	0.10
PDQ total preoperative	0.002	0.01
VAS preoperative	0.009	0.18	−0.003	−0.016, 0.010	0.62

Abbreviations: BMI, body mass index; CI, confidence interval; EQ-5D, EuroQol-5 Dimensions; PDQ, Pain Disability Questionnaire; PHQ-9, Patient Health Questionnaire; QALY, quality-adjusted life-years; VAS, visual analog scale.

Note: Negative coefficients indicate less change in EQ-5D. For the multivariable model, R ² = 0.33 and root mean square error = 0.18.