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Table 3 Average retention rates by study characteristics

From: Recruitment and retention in obesity prevention and treatment trials targeting minority or low-income children: a review of the clinical trials registration database

  Number of studies Study enrollmenta Study retentionb Average retention rates
Race or ethnicity
 Hispanic 5 586 511 82.8
 African American 10 1331 1059 83.5
 African American, white and other 8 1927 1763 92.1
Intervention target
 Children 3 413 388 91.1
 Children and parent 20 3431 2945 85.6
Body weight status
 Overweight or obese 9 1581 1314 79.6
 All weights 10 1523 1334 90.0
 Body weight status not measured 4 740 685 92.6
Study type
 Prevention 10 1523 1334 90.0
 Treatment 13 2321 1999 83.6
Intervention length
 <1 year 16 1658 1461 88.6
 ≥1 year 7 2186 1872 81.1
Study type and treatment length
 Prevention <1 year 7 707 614 90.4
 Prevention ≥1 year 3 816 720 88.8
 Treatment <1 year 9 951 847 87.2
 Treatment ≥1 year 4 1073 873 74.0
Primary outcome
 BMI or anthropometrics 10 2342 2026 82.9
 Other (behavior, physiology, etc.) 13 1502 1307 89.0
Intervention settingc
 School 5 1273 1151 91.7
 Home or community 15 2410 2051 85.5
 Laboratory 2 126 102 81.1
Main intervention group
 Nutrition or physical activity 4 755 712 92.8
 Nutrition and physical activity 19 3089 2621 85.0
Study design
 Randomized controlled trial 19 2739 2440 89.3
 Cluster randomized controlled trial 2 745 656 75.6
 Controlled trial 1 235 136 57.9
 Trial without control 1 125 101 80.8
Mean age of childrend
 <12 years 15 2708 2333 86.2
 ≥12 years 8 1136 1000 86.7
Number of intervention sessionse
 ≤12 7 752 636 86.3
 ≥13 15 2840 2445 85.5
Sample size
 <100 9 493 435 86.9
 ≥100 14 3351 2898 86.0
  1. aThe sum of numbers of participants enrolled in individual studies
  2. bThe sum of numbers of participants retained in individual studies
  3. cIntervention setting was not reported in the study by Weigensberg et al. [28]
  4. d<12 years group includes one study with participants aged 8–14 years; ≥12 years group includes one study with participants aged 9–14 years, one study with participants aged 10–17 years and two studies with participants aged 11–16 years
  5. eNumber of intervention sessions was not reported in the study by Azevedo et al. [17]