The clinical course of low back pain: a meta-analysis comparing outcomes in randomised clinical trials (RCTs) and observational studies

Table 3 Comparison of population characteristics of included RCTs and observational cohort studies

		Cohort studies	RCTs^a
Publication year		1994-2012	1993-2012
Sample size, Median (range)		368 (60, 2872)	128 (28, 681)^b
Sample size, Median (range)		368 (60, 2872)	67 (12, 340)^c
Age, mean ^d (SD)		43 (4.1)	44 (7.9)
Female, mean percentage (SD)		52 (4.8)	53 (16.9)
Type of pain, n (%)	Acute	5 (26)	34 (20)
	Chronic	2(11)	94 (57)
	Mixed	12(63)	31 (19)
	Unclear	0	6 (4)
Baseline pain intensity, mean ^d (SD)		49.6 (12.7)	49.9 (12.9)

^aRCTs that provided data on pain intensity outcome. ^bSample size of RCT. ^cSample size of arm. ^dMean of all cohort/RCT means.

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