Table 2.
Factors associated with survey response over 3 follow-up surveys using baseline (Survey 1) characteristics as explanatory variables (N=17,012; 187 participants were excluded due to missing data). The included explanatory factors for predicting response at follow-up surveys were model 1 (survey), model 2 (survey + recruitment method), and model 3 (survey + recruitment method + other characteristics; eg, selected demographic/health factors).
| Baseline characteristics | Model 1 | Model 2 | Model 3 | ||||
| PR (95% CI)a | P value | PR (95% CI) | P value | PR (95% CI) | P value | ||
| Survey | |||||||
|
|
2 (2014) | 1 | —b | 1 | — | 1 | — |
| 3 (2015) | 0.79 (0.78-0.80) | <.001 | 0.79, (0.78-0.80) | <.001 | 0.80 (0.79-0.81) | <.001 | |
| 4 (2016) | 0.79 (0.78-0.80) | <.001 | 0.80 (0.79-0.81) | <.001 | 0.80 (0.79-0.81) | <.001 | |
| Recruitment method | |||||||
|
|
— | — | 1 | — | 1 | — | |
| Other social media | — | — | 1.06 (1.01-1.11) | .0114 | 1.04 (0.99-1.08) | .10 | |
| Referral | — | — | 1.14 (1.11-1.18) | <.001 | 1.11 (1.07-1.15) | <.001 | |
| Traditional media | — | — | 1.22 (1.18-1.26) | <.001 | 1.18 (1.14-1.22) | <.001 | |
| Fashion promotion | — | — | 0.97 (0.94-1.00) | .0321 | 0.94 (0.91-0.97) | <.001 | |
| Baseline age | |||||||
|
|
18-20 years | — | — | — | — | 1 | — |
| 21-23 years | — | — | — | — | 1.08 (1.06-1.10) | <.001 | |
| Area of residence | |||||||
|
|
Major cities | — | — | — | — | 1 | — |
| Inner regional | — | — | — | — | 1.01 (0.98-1.03) | .59 | |
| Outer regional and remote areas | — | — | — | — | 0.97 (0.93-1.01) | .11 | |
| Education | |||||||
|
|
Grade 12 or more | — | — | — | — | 1 | — |
| Less than Grade 12 | — | — | — | — | 0.80 (0.76-0.84) | <.001 | |
| Income management | |||||||
|
|
Easy/not too bad/difficult sometimes | — | — | — | — | 1 | — |
| Impossible/difficult all the time | — | — | — | — | 0.95 (0.93-0.97) | <.001 | |
| Obesity | |||||||
|
|
Not obese (BMIc<30) | — | — | — | — | 1 | — |
| Obese (BMI ≥ 30 or more) | — | — | — | — | 0.95 (0.92-0.98) | .0035 | |
| Smoking status | |||||||
|
|
Nonsmoker/exsmoker | — | — | — | — | 1 | — |
| Current smoker | — | — | — | — | 0.82 (0.79-0.85) | <.001 | |
| Self-rated health | |||||||
|
|
Excellent/very good/good | — | — | — | — | 1 | — |
| Fair/poor | — | — | — | — | 0.99 (0.96-1.02) | .61 | |
| Psychological distress | |||||||
|
|
Not very high (K10 score<30) | — | — | — | — | 1 | — |
| Very high distress (K10 score ≥30) | — | — | — | — | 0.96 (0.93-0.98) | .0016 | |
aPR (95% CI): prevalence ratio with 95% CI.
bNot applicable.
cBMI: body mass index.