Table 5.
Factors associated with participation in the extended phase
| Model C: paper-and-pencil participants (asked to switch to online mode) |
Model D: online participants (asked to stay in the study) |
|||
|---|---|---|---|---|
| Beta | Odds ratio | Beta | Odds ratio | |
| Age at baseline (per 10 years increase) | not selected in this model | 0.24 | 1.27 | |
| Marital status: unmarried vs. married |
not selected in this model | 0.27 | 1.31 | |
| WHO-5 well-being index (per 10 points increase) | not selected in this model | 0.01 | 1.01 | |
| PSS score (per 1 point increase) | −0.02 | 0.98 | −0.01 | 0.99 |
| ID-Screen (per 1 point increase) | 0.01 | 1.01 | 0.04 | 1.05 |
| Time between invitation and return of the filled informed consent form (per week) |
not selected in this model | 0.05 | 1.05 | |
| Number of questionnaires returned during initial phasea
(per questionnaire) |
0.19 | 1.21 | 0.43 | 1.54 |
| Number of times a participant had to receive reminder emails during the initial phase (per reminder) |
not applicable to paper-and-pencil participants |
−0.27 | 0.76 | |
Variables were selected using the least absolute shrinkage and selection operator method in logistic regression
ID Screen: mean score based on infections and infection-associated symptoms in the last 12 months (score ranges from 0 [no infections in the last 12 months] to 46 [more than 42 infections in the last 12 months])
PSS: perceived stress scale (score ranges from 0 [very low stress level] to 16 [very high stress level])
aPaper-and-pencil participants received a total of two questionnaires; online participants received a total of eleven questionnaires