Table 3.

Area under curve subgroup results from the adjusted^* as-treated Oswestry Disability Index (ODI) outcome analysis for combinations of the six significant treatment effect predictors (time weighted average 4 year treatment effects).

	N	Surgical	Non-operative	Treatment Effect† (95% CI)
Non-smokers with ODI ≤ 56, foraminal stenosis, neurological deficit, predominant leg pain, and no lifting at work	35	−23.8 (2.7)	0.3 (3.1)	−24.1 (−30.2, −18)
Smokers with ODI > 56	23	−0.9 (3.8)	−4.5 (5.2)	3.6 (−5.6, 12.8)
Others	576	−20.2 (0.7)	−9.9 (0.8)	−10.2 (−12.1, −8.4)
p-value		<0.001	0.003	<0.001

^*Adjusted for center, age, gender, baseline ODI score, income, treatment preference, duration of symptoms, compensation, smoking status, BMI, baseline Stenosis Bothersomeness, joint, stomach and bowel problems.

^†Treatment effect is the difference between the surgical and non-operative mean change from baseline. Analysis is done using a mixed model with a random subject intercept term. Treatment is a time-varying covariate where a patients’ experience prior to surgery is attributed to the non-operative arm and time is measured from enrollment and his/her post-surgery outcomes are attributed to the surgical arm and time is measured from time of surgery.