Table 1 Baseline description of the sample within different SP frequency groups*

Number of participants

9422

4667

1411

1101

2243

Age

57.68 ± 8.24

58.06 ± 8.05

56.44 ± 7.94

56.72 ± 8.34

58.17 ± 8.64

Gender

  Male

4362 (46.30%)

2130 (45.64%)

714 (50.60%)

586 (53.22%)

932 (41.55%)

  Female

5060 (53.70%)

2537 (54.36%)

697 (49.40%)

515 (46.78%)

1311 (58.45%)

Education levels

  Less than lower secondary

8362 (88.75%)

4298 (92.09%)

1239 (87.81%)

934 (84.83%)

1891 (84.31%)

  Upper secondary & vocational training

933 (9.90%)

344 (7.37%)

154 (10.91%)

146 (13.26%)

289 (12.88%)

  Tertiary

127 (1.35%)

25 (0.54%)

18 (1.28%)

21 (1.91%)

63 (2.81%)

Marital status

  Divorced or widowed

951 (10.09%)

476 (10.20%)

120 (8.50%)

89 (8.08%)

266 (11.86%)

  Married

8471 (89.91%)

4191 (89.80%)

1291 (91.50%)

1012 (91.92%)

1977 (88.14%)

Hukou status

  Agricultural

7711 (81.85%)

4009 (85.92%)

1182 (83.77%)

880 (79.93%)

1640 (73.12%)

  Non-agricultural

1647 (17.48%)

625 (13.39%)

223 (15.80%)

213 (19.35%)

586 (26.13%)

  Other

63 (0.67%)

32 (0.69%)

6 (0.43%)

8 (0.73%)

17 (0.76%)

Rural/urban residence

  Rural

6153 (65.30%)

3160 (67.71%)

974 (69.03%)

717 (65.12%)

1302 (58.05%)

  Urban

3269 (34.70%)

1507 (32.29%)

437 (30.97%)

384 (34.88%)

941 (41.95%)

Morbidity

  None

2843 (30.17%)

1397 (29.93%)

431 (30.55%)

337 (30.61%)

678 (30.23%)

  Single

2805 (29.77%)

1419 (30.40%)

442 (31.33%)

309 (28.07%)

635 (28.31%)

  Morbidity

3774 (40.06%)

1851 (39.66%)

538 (38.13%)

455 (41.33%)

930 (41.46%)

Public health insurance coverage

  Not covered

566 (6.02%)

289 (6.21%)

69 (4.90%)

57 (5.18%)

151 (6.76%)

  Covered

8834 (93.98%)

4367 (93.79%)

1340 (95.10%)

1043 (94.82%)

2084 (93.24%)

Current work status

  Not working

2319 (24.68%)

1036 (22.27%)

252 (17.89%)

242 (22.04%)

789 (35.25%)

  Working

7078 (75.32%)

3616 (77.73%)

1157 (82.11%)

856 (77.96%)

1449 (64.75%)

Alcohol intake

  Do not drink

6308 (66.95%)

3246 (69.55%)

858 (60.81%)

668 (60.67%)

1536 (68.48%)

  Drink

3114 (33.05%)

1421 (30.45%)

553 (39.19%)

433 (39.33%)

707 (31.52%)

Smoking status

  Never

5810 (61.67%)

2939 (62.99%)

794 (56.27%)

620 (56.31%)

1457 (64.96%)

  Quit now

752 (7.98%)

362 (7.76%)

124 (8.79%)

104 (9.45%)

162 (7.22%)

  Smoke

2859 (30.35%)

1365 (29.25%)

493 (34.94%)

377 (34.24%)

624 (27.82%)

Household per capita consumption

  Low

3178 (39.28%)

1699 (42.71%)

489 (39.79%)

344 (36.13%)

646 (33.45%)

  Low to middle

2369 (29.28%)

1192 (29.96%)

363 (29.54%)

259 (27.21%)

555 (28.74%)

  Middle

1706 (21.09%)

767 (19.28%)

260 (21.16%)

230 (24.16%)

449 (23.25%)

  High

837 (10.35%)

320 (8.04%)

117 (9.52%)

119 (12.50%)

281 (14.55%)