Table 1

Quality assessment using Epidemiological Appraisal Instrument:36 number of studies (%)

Walking CSInjury CS/Long/TS (n=25)Injury CC/CCROSS (n=11)
NoPartialYesNA/UTDNoPartialYesNA/UTDNoPartialYesNA/UTD
1. Description
 Hypothesis/objective(s)1 (2)4 (8)45 (90)00 (0)1 (4)24 (96)003 (27)8 (73)0
 Exposures clear01 (2)7 (14)42 (84)0 (0)0 (0)8 (32)17 (68)002 (18)9 (82)
 Outcome clear04 (8)46 (92)00 (0)0 (0)25 (100)00011 (100)0
 Study design*024 (48)26 (52)01 (4)19 (76)5 (20)01 (9)2 (18)8 (73)0
 Population source/sampling frame2 (4)7 (14)41 (82)00 (0)0 (0)25 (100)00011 (100)0
 Eligibility criteria5 (10)10 (20)35 (70)00 (0)0 (0)25 (100)00011 (100)0
 Participation rate/record availability15 (30)1 (2)34 (68)00 (0)0 (0)25 (100)0006 (55)5 (45)
 Participant characteristics12 (24)037 (74)1 (2)6 (24)2 (8)17 (68)00011 (100)0
 Non-participant characteristics42 (84)08 (16)000025 (100)02 (18)09 (82)
 Covariates–individual variables1 (2)5 (10)40 (80)00 (0)0 (0)8 (32)17 (68)1 (9)1 (9)9 (82)0
 Covariates–environment
  Variables1 (2)2 (4)40 (80)7 (14)0 (0)4 (16)14 (56)7 (28)2 (18)09 (82)0
 Statistical methods1 (2)3 (6)46 (92)01 (4)0 (0)24 (96)002 (18)9 (82)0
 Main findings01 (2)49 (98)00 (0)0 (0)25 (100)00011 (100)0
 Estimates of random variability12 (24)038 (76)016 (64)0 (0)9 (36)02 (18)09 (82)0
 Estimates of statistical parameters0050 (100)02 (8)0 (0)23 (92)00011 (100)0
 Sample size calculations49 (98)0000025 (100)002 (18)9 (82)
2. Methods quality
 2.1 Subject selection
  Controls comparable with cases0011 (100)0
  Participation rate/record availability adequacy14 (28)15 (30)6 (12)15 (30)00025 (100)01 (9)4 (36)6 (55)
  Cases/controls recruited over same period of time006 (55)5 (45)
  Newly incident cases accounted for00011 (100)
  Subject losses/unavailable records42 (84)2 (4)2 (4)4 (8)001 (4)24 (96)00011 (100)
 2.2 Measurement
  Exposure/covariate measure reliability2 (4)9 (18)3 (6)35 (70)00025 (100)00011 (100)
  Exposure/covariate measure valid07 (14)2 (4)41 (82)00025 (100)00011 (100)
  Exposure assessment similar for case/controls0011 (100)0
  Exposure prior to disease00011 (100
  Observers blinding002 (18)9 (82)
  Subject blinding00011 (100)
  Outcome measures reliable1 (2)4 (8)4 (8)41 (82)00025 (100)00011 (100)
  Outcome measures valid05 (10)045 (90)1 (4)0024 (96)00011 (100)
  Standard methods of assessing outcome both case/controls0011 (100)0
  Observations over same time for case/controls0047 (64)
 2.3 Data analysis
  Prior history of disease accounted for00011 (100)
  Adequate covariate adjustment–individual02 (4)44 (88)4 (8)008 (32)17 (68)01 (9)9 (82)1 (9)
  Adequate covariate adjustment–environment0042 (84)8 (16)0017 (68)8 (32)2 (18)09 (82)0
  Time between exposure and outcome same cases/controls00011 (100)
  Data reported by subgroups15 (30)035 (70)07 (28)018 (72)03 (27)08 (73)0
 2.4 Generalisation
  To eligible population13 (26)16 (32)6 (12)15 (30)00025 (100)01 (4)4 (36)6 (55)
  To other relevant populations13 (26)16 (32)6 (12)15 (30)00025 (100)01 (4)4 (36)6 (55)
  • Shading=not applicable for study design.

  • CC, case control; CCROSS, case crossover; CS, cross-sectional; Long, longitudinal; NA/UTD, not applicable/unable to determine; TS, time series.