Table 2. Number of participants in the JASTIS study (Cohort 1, 2 and 3).
| Characteristics at baseline | Wave 1 | Wave 2 | Wave 3 | Wave 4 |
| January 31 to February 17, 2015 |
January 29 to February 15, 2016 |
January 27 to February 27, 2017 |
January 26 to March 20, 2018 |
|
| Number of participants | Respondents of follow-up survey (%) |
Respondents of follow-up survey (%) |
Respondents of follow-up survey (%) |
|
| Cohort 1: designation only for sex and age | 8,240 | 5,366 (65.1) | 4,217 (51.2) | 3,873 (47.0) |
| men, 15–19 years old | 443 | 95 (21.4) | 51 (11.5) | 42 (9.5) |
| men, 20–29 years old | 720 | 429 (59.6) | 305 (42.4) | 274 (38.1) |
| men, 30–39 years old | 728 | 507 (69.6) | 410 (56.3) | 375 (51.5) |
| men, 40–49 years old | 740 | 571 (77.2) | 467 (63.1) | 443 (59.9) |
| men, 50–59 years old | 722 | 550 (76.2) | 458 (63.4) | 439 (60.8) |
| men, 60–69 years old | 731 | 610 (83.4) | 511 (69.9) | 489 (66.9) |
| women, 15–19 years old | 438 | 128 (29.2) | 86 (19.6) | 78 (17.8) |
| women, 20–29 years old | 742 | 384 (51.8) | 274 (36.9) | 240 (32.3) |
| women, 30–39 years old | 737 | 454 (61.6) | 369 (50.1) | 309 (41.9) |
| women, 40–49 years old | 747 | 522 (69.9) | 407 (54.5) | 363 (48.6) |
| women, 50–59 years old | 739 | 542 (73.3) | 416 (56.3) | 382 (51.7) |
| women, 60–69 years old | 753 | 574 (76.2) | 463 (61.5) | 439 (58.3) |
| Cohort 2: e-cigarette/heat-not-burn tobacco ever users |
2,188 | 1,387 (63.4) | 1,480 (67.6) | 1,375 (62.8) |
| current user | 727 | 405 (55.7) | 505 (69.5) | 462 (63.5) |
| former regular user | 727 | 464 (63.8) | 506 (69.6) | 464 (63.8) |
| former non-regular user | 734 | 518 (70.6) | 469 (63.9) | 449 (61.2) |
| Cohort 3: smokers without e-cigarette/ Heat-not-burn tobacco use experience |
724 | 547 (75.6) | 470 (64.9) | 433 (59.8) |
| ↓ Sample reconstruction | ||||
| Sum of cohort 1, 2 and 3 | 11,152 | 7,300 (65.5) | 6,167 (55.3) | 5,681 (50.9) |
| Combustible cigarette smoking category | ||||
| current smoker | 3,279 | 2,276 (69.4) | 2,078 (63.4) | 1,945 (59.3) |
| former smoker | 2,301 | 1,559 (67.8) | 1,356 (58.9) | 1,262 (54.8) |
| never smoker | 5,572 | 3,465 (62.2) | 2,733 (49.0) | 2,474 (44.4) |
| E-cigarette/Heat-not-burn tobacco category | ||||
| current user | 779 | 431 (55.3) | 521 (66.9) | 475 (61.0) |
| former user | 1,849 | 1,208 (65.3) | 1,152 (62.3) | 1,071 (57.9) |
| never user | 8,524 | 5,661 (66.4) | 4,494 (52.7) | 4,135 (48.5) |
Response rates in parentheses. Numbers of participants after exclusion of cases with data discrepancies.