Table 1.
Participants’ demographic characteristics.
| Variables | 2004 (n = 2181) |
2006 (n = 2399) |
2009 (n = 2718) |
2011 (n = 3745) |
2015 (n = 4564) |
|---|---|---|---|---|---|
| Age (years) | |||||
| 60–69 | 1259 (57.7) | 1367 (57.0) | 1546 (56.9) | 2266 (60.5) | 2822 (61.8) |
| 70–79 | 734 (33.7) | 815 (34.0) | 900 (33.1) | 1128 (30.1) | 1306 (28.6) |
| ≥80 | 188 (8.6) | 217 (9.0) | 272 (10.0) | 351 (9.4) | 436 (9.6) |
| Gender | |||||
| Male | 1024 (47.0) | 1124 (46.9) | 1275 (46.9) | 1775 (47.4) | 2136 (46.8) |
| Female | 1157 (53.0) | 1275 (53.1) | 1443 (53.1) | 1970 (52.6) | 2428 (53.2) |
| Education level | |||||
| Below primary school a | 1116 (51.4) | 1297 (54.4) | 1324 (48.9) | 1573 (42.1) | 1497 (32.8) |
| Primary school | 525 (24.2) | 451 (18.9) | 633 (23.4) | 795 (21.3) | 1043 (22.9) |
| Middle school | 260 (12.0) | 307 (12.9) | 401 (14.8) | 716 (19.2) | 1044 (22.9) |
| High school or above | 272 (12.5) | 331 (13.9) | 351 (13.0) | 651 (17.4) | 980 (21.5) |
| Nationality | |||||
| Han | 1933 (88.6) | 2109 (87.9) | 2351 (86.8) | 3357 (89.8) | 4078 (90.1) |
| The minority | 248 (11.4) | 290 (12.1) | 358 (13.2) | 381 (10.2) | 448 (9.9) |
| BMI (kg/m2) | |||||
| <20 | 444 (21.5) | 476 (21.2) | 494 (19.1) | 571 (15.6) | 493 (11.8) |
| 20–26.9 | 1318 (63.9) | 1452 (64.7) | 1710 (66.0) | 2463 (67.1) | 2825 (67.5) |
| ≥27 | 300 (14.5) | 317 (14.1) | 386 (14.9) | 637 (17.4) | 868 (20.7) |
| Place of residence | |||||
| Urban | 839 (38.5) | 892 (37.2) | 979 (36.0) | 1599 (42.7) | 1915 (42.0) |
| Rural | 1342 (61.5) | 1507 (62.8) | 1739 (64.0) | 2146 (57.3) | 2649 (58.0) |
| Geographical region | |||||
| Western region | 596 (27.1) | 650 (27.1) | 730 (26.9) | 1011 (27.0) | 1218 (26.7) |
| Central region | 665 (30.4) | 729 (30.8) | 837 (30.8) | 939 (25.1) | 1068 (23.4) |
| Eastern region | 554 (25.4) | 609 (25.4) | 681 (25.1) | 1279 (34.2) | 1680 (36.8) |
| Northeast region | 366 (16.8) | 411 (17.1) | 470 (17.3) | 516 (13.8) | 598 (13.1) |
Sample sizes of the demographic characteristics variables may not sum to n = 15,607 due to missing values. a Below primary school group includes participants who were uneducated or did not know their own education level. BMI, body mass index.