eTable 1. Type of response by study arm, n (%).
| Written | Telephone | Total | |
| Initial sample | 19,213 (100) | 11,476 (100) | 30,689 (100) |
| Evaluable questionnaires following data validation | 5467 (28.5) | 3579 (31.2) | 9046 (29.5) |
| Non-evaluable questionnaires following data validation | 49 (0.3) | 14 (0.1) | 63 (0.2) |
| Response status unknown | 11,735 (61.1) | 1 (0.0) | 11,736 (38.2) |
| Neutral dropouts | 1423 (7.4) | 1575 (13.7) | 2998 (9.8) |
| – Target person unknown | 1402 (7.3) | 256 (2.2) | 1658 (5.4) |
| – Telephone number invalid | – | 1193 (10.4) | 1193 (3.9) |
| – Target person does not speak sufficient German | 9 (0.1) | 70 (0.6) | 79 (0.3) |
| – Target person not in target group | 7 (0.0) | 45 (0.4) | 52 (0.2) |
| – Target person deceased | 5 (0.0) | 11 (0.1) | 16 (0.1) |
| Systematic dropouts | 539 (2.8) | 6307 (55.0) | 6846 (22.3) |
| – Refusal | 235 (1.2) | 2934 (25.6) | 3169 (10.3) |
| – Not contactable | 281 (1.5) | 3094 (27.0) | 3375 (11.0) |
| – Health problems | 13 (0.1) | 50 (0.4) | 63 (0.2) |
| – Target person wanted to respond* | 10 (0.1) | 229 (2.0) | 239 (0.8) |
*Target person wished to complete the questionnaire in writing, or complete it online or in a telephone interview, but eventually did not