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

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

   Cohort studies RCTsa
Publication year   1994-2012 1993-2012
Sample size, Median (range)   368 (60, 2872) 128 (28, 681)b
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)
  1. aRCTs that provided data on pain intensity outcome. bSample size of RCT. cSample size of arm. dMean of all cohort/RCT means.