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Table 2 Comparison of responders and non-responders to trial invite

From: Response bias to a randomised controlled trial of a lifestyle intervention in people at high risk of cardiovascular disease: a cross-sectional analysis

  All invited n=8902a Responded to invitation
n = 1489
Did not respond to invitation
n = 7413
Response rate (%) Unadjusted OR for response to mailout
(95% CI)
Adjusted OR for response to mailout
(95% CI)
Test for trend
(p)
Age at invitation (years) 67.3 (5.7) 68.1 (5.1) 67.2 (5.8)   1.14 (1.08, 1.21)b 1.19 (1.12, 1.26)b < 0.001
Age at invitation
 40-59 yrs 976 (11.0%) 124 (8.4%) 852 (11.6%) 12.7    
 60-64 yrs 1462 (16.4%) 200 (13.5%) 1262 (17.0%) 13.7    
 65-69 yrs 2989 (33.6%) 536 (36.0%) 2453 (33.1%) 17.9    
 70-75 yrs 3475 (39.0%) 629 (42.2%) 2846 (38.4%) 18.1    
Sex
 Female 1847 (20.7%) 291 (19.5%) 1556 (21.0%) 15.8 1.00 1.00  
 Male 7055 (79.3%) 1198 (80.5%) 5857 (79.0%) 17.0 1.07 (0.93, 1.23) 1.25 (1.08, 1.45) 0.004
Ethnicity < 0.001c
 White 6223 (69.9%) 1128 (75.8%) 5095 (68.7%) 18.1 1.00 1.00  
 Black African or Caribbean 272 (3.1%) 34 (2.3%) 238 (3.2%) 12.5 0.74 (0.50, 1.07) 0.67 (0.45, 0.98) 0.040
 South Asian 578 (6.5%) 98 (6.6%) 480 (6.5%) 17.0 0.90 (0.70, 1.14) 1.08 (0.84, 1.38) 0.542
 Other Asian 240 (2.7%) 31 (2.1%) 209 (2.8%) 12.9 0.69 (0.47, 1.03) 0.69 (0.46, 1.02) 0.066
 Other/Mixed 147 (1.7%) 16 (1.1%) 131 (1.8%) 10.9 0.62 (0.36, 1.05) 0.61 (0.36, 1.04) 0.072
 Missing 1442 (16.2%) 182 (12.2%) 1260 (17.0%) 12.6 0.58 (0.48, 0.69) 0.55 (0.46, 0.66) < 0.001
IMD 2010 quintile < 0.001c
 1 (least deprived) 1407 (15.8%) 293 (19.7%) 1114 (15.0%) 20.8 1.00 1.00  
 2 1531 (17.2%) 285 (19.1%) 1246 (16.8%) 18.6 0.86 (0.70, 1.04) 0.87 (0.72, 1.07) 0.190
 3 1616 (18.2%) 315 (21.2%) 1301 (17.6%) 19.5 0.80 (0.65, 0.98) 0.85 (0.69, 1.05) 0.139
 4 2725 (30.6%) 420 (28.2%) 2305 (31.1%) 15.4 0.64 (0.52, 0.79) 0.70 (0.56, 0.87) 0.001
 5 (most deprived) 1604 (18.0%) 171 (11.5%) 1433 (19.3%) 10.7 0.46 (0.23, 0.33) 0.52 (0.40, 0.68) < 0.001
 Unknown 19 (0.2%) 5 (0.3%) 14 (0.2%) 26.3    
QRisk2 score (%) 25.2 (5.0) 24.6 (4.5) 25.3 (5.1)   0.86 (0.81, 0.92)d 0.82 (0.77, 0.88)d < 0.001
 20–24.9% 5357 (60.2%) 968 (65.0%) 4389 (59.2%) 18.1    
 25–29.9% 2245 (25.2%) 347 (23.3%) 1898 (25.6%) 15.5    
 > 30% 1300 (14.6%) 174 (11.7%) 1126 (15.2%) 13.4    
  1. OR odds ratio, CI confidence intervals, IMD Index of Multiple Deprivation
  2. Data are presented as mean (SD) or n (%) unless otherwise stated
  3. aAll patients invited to participate in the trial from GP practice sites at which it was possible to extract anonymised data
  4. bOR per 5 year increase in age
  5. cChi square test for independence
  6. dOR per 5% increase in QRisk2 score