Table 3

Results of longitudinal random effects models evaluating main effects, without and with covariate adjustment

Predictor or covariate	Without covariate adjustment			With covariate adjustment

	b	SE	p value	b	SE	p value
Rand-36 physical component score

Time	0.022	0.002	< 0.001	0.019	0.003	< 0.001

Exercise score	0.600	0.186	0.001	0.31	0.35	0.37

Education

Some college				−0.48	2.08	0.82

College				3.62	1.89	0.06

Postgraduate				2.14	1.95	0.27

Employment

Currently working				6.73	1.73	< 0.001

Retired				−1.15	1.76	0.51

Rand-36 mental component score

Time	0.009	0.002	< 0.001	0.004	0.003	0.16

Exercise score	0.367	0.172	0.033	0.46	0.37	0.21

Education

Some college				6.96	2.29	< 0.001

College				3.67	2.09	0.08

Postgraduate				5.62	2.15	0.01

Employment

Currently working				0.62	1.85	0.74

Retired				7.06	1.89	< 0.001

PROMIS Pain Interference score^*

Time	0.030	0.002	< 0.001	0.026	0.003	< 0.001

Exercise score	0.376	0.182	0.039	0.35	0.31	0.26

Education

Some college				1.13	1.76	0.52

College				2.81	1.60	0.08

Postgraduate				1.37	1.65	0.40

Employment

Currently working				1.34	1.50	0.37

Retired				1.27	1.51	0.40

Oswestry Disability Index score^*

Time	0.027	0.002	< 0.001	0.023	0.003	< 0.001

Exercise score	0.584	0.163	< 0.001	0.78	0.29	0.01

Education

Some college				2.65	1.76	0.13

College				3.93	1.61	0.01

Postgraduate				2.56	1.65	0.12

Employment

Currently working				4.65	1.47	< 0.001

Retired				4.23	1.48	< 0.001

Numeric Rating Scale^*

Time	0.030	0.002	< 0.001	0.024	0.003	< 0.001

Exercise score	−0.016	0.182	0.93	0.21	0.32	0.51

Education

Some college				1.73	1.88	0.36

College				2.81	1.72	0.10

Postgraduate				3.23	1.76	0.07

Employment

Currently working				0.07	1.58	0.96

Retired				0.12	1.59	0.94

PROMIS = Patient-Reported Outcome Measurement Information System; Rand-36 = Medical Outcomes Study 36-Item Short-Form Survey; SE = standard error.
↵* Score recoded such that high scores reflect better functioning.
Each outcome is standardized to have mean 50, standard deviation 10.