Table 2

Baseline demographics

	Q1 (n=66)	Q2 (n=65)	Q3 (n=65)	Q4 (n=65)	Total (n=261)	P value
Age mean	35.3	46.2	52.6	62.4	49.1	<0.001*
(SE)	(0.7)	(0.2)	(0.3)	(0.8)	(0.7)
Age median	37	47	53	60	49
(Range)	(22–43)	43–49	49–56	56–82	22–82
BMI mean	28.2	29.3	28.5	27.9	28.4	0.34*
(SE)	(0.6)	(0.6)	(0.5)	(0.6)	(0.6)
Sex % female	47.0	46.2	47.7	61.5	50.6	0.24†
Baseline ODI mean	39.4	42.6	41.5	38.9	40.6	0.29*
(SE)	(1.6)	(1.4)	(1.6)	(1.6)	(0.8)
Baseline EQ-5D mean	0.552	0.523	0.532	0.568	0.544	0.64*
(SE)	0.023	0.028	0.027	0.027	0.013

*Significance tested using one way ANOVA.
†Significance tested using χ².
ANOVA, analysis of variance; BMI, body mass index; EQ-5D, EuroQol 5-Dimension; ODI, Oswestry Disability Index.