Table 1 Characteristic of participants (N = 302,510)
| Â | Participants with a history of pregnancy | ||||||||
|---|---|---|---|---|---|---|---|---|---|
Total | Nulligravid | Total | 0 | 1 | 2 | ≥3 | Missing | P-value | |
Number of females participants | 302,510 (100.00) | 2,881 (0.95) | 299,629 (100.00) | 115,283 (38.48) | 93,409 (31.18) | 57,049 (19.04) | 33,838 (11.30) | 50 (0.02) | - |
Age, median (IQR) | 50.92 (42.60 – 58.78) | 49.98 (40.88 – 59.56) | 50.93 (42.62 – 58.77) | 51.49 (42.43 – 59.43) | 50.68 (42.56 – 58.55) | 50.32 (42.66 – 57.91) | 50.91 (43.26 – 58.18) | 51.54 (40.00 – 61.97) | 0.0001 |
RA, n (%) | |||||||||
 No | 294,935 (97.50) | 2,810 (97.54) | 292,125 (97.50) | 112,806 (97.85) | 91,023 (97.45) | 55,449 (97.20) | 32,798 (96.93) | 49 (98.00) | <0.0001 |
 Yes | 7,575 (2.50) | 71 (2.46) | 7,504 (2.50) | 2,477 (2.15) | 2,386 (2.55) | 1,600 (2.80) | 1,040 (3.07) | 1 (2.00) |  |
Age at RA diagnosis, median (IQR) | 45.00 (37.00 – 53.00) | 40.00 (35.00 – 56.00) | 45.00 (37.00 – 53.00) | 46.00 (38.00 – 53.00) | 45.00 (37.00 – 53.00) | 45.00 (37.00 – 52.00) | 45.00 (37.00 – 52.00) | 63.00 (63.00 – 63.00) | 0.0115 |
Region, n (%) | |||||||||
 Urban | 134,828 (44.57) | 1,755 (60.92) | 133,073 (44.41) | 36,400 (31.57) | 46,732 (50.03) | 32,222 (56.48) | 17,696 (52.30) | 23 (46.00) | <0.0001 |
 Rural | 167,682 (55.43) | 1,126 (39.08) | 166,556 (55.59) | 78,883 (68.43) | 46,677 (49.97) | 24,827 (43.52) | 16,142 (47.70) | 27 (54.00) |  |
Education, n (%) | |||||||||
 Primary or below | 171,580 (56.72) | 1,248 (43.32) | 170,332 (56.85) | 76,851 (66.66) | 49,867 (53.39) | 26,863 (47.09) | 16,722 (49.42) | 29 (58.00) | <0.0001 |
 Secondary | 117,491 (38.84) | 1,225 (42.52) | 116,266 (38.80) | 35,272 (30.60) | 38,854 (41.60) | 26,792 (46.96) | 15,330 (45.30) | 18 (36.00) |  |
 Tertiary | 13,439 (4.44) | 408 (14.16) | 13,031 (4.35) | 3,160 (2.74) | 4,688 (5.02) | 3,394 (5.95) | 1,786 (5.28) | 3 (6.00) |  |
Occupation, n (%) | |||||||||
 Agriculture | 122,672 (40.55) | 747 (25.93) | 121,925 (40.69) | 59,585 (51.69) | 32,916 (35.24) | 17,627 (30.90) | 11,772 (34.79) | 25 (50.00) | <0.0001 |
 Factory | 32,160 (10.63) | 336 (11.66) | 31,824 (10.62) | 9,823 (8.52) | 12,477 (13.36) | 6,869 (12.04) | 2,646 (7.82) | 9 (18.00) |  |
 Administrative/Managerial/Sales | 19,093 (6.31) | 274 (9.51) | 18,819 (6.28) | 4,839 (4.20) | 6,822 (7.30) | 4,644 (8.14) | 2,510 (7.42) | 4 (8.00) |  |
Professional/ Technical | 7,960 (2.63) | 224 (7.78) | 7,736 (2.58) | 1,890 (1.64) | 2,684 (2.87) | 2,027 (3.55) | 1,135 (3.35) | 0 (0.00) | Â |
 Unemployed/Retired | 61,773 (20.42) | 773 (26.83) | 61,000 (20.36) | 15,860 (13.76) | 21,093 (22.58) | 15,501 (27.17) | 8,537 (25.23) | 9 (18.00) |  |
 Housewife | 47,578 (15.73) | 432 (14.99) | 47,146 (15.73) | 20,013 (17.36) | 13,589 (14.55) | 7,879 (13.81) | 5,664 (16.74) | 1 (2.00) |  |
 Self-employed/Others | 11,274 (3.73) | 95 (3.30) | 11,179 (3.73) | 3,273 (2.84) | 3,282 (4.10) | 2,502 (4.39) | 1,574 (4.65) | 2 (4.00) |  |
Marital status, n (%) | |||||||||
 Married | 269,166 (88.98) | 1,902 (66.02) | 267,264 (89.20) | 102,986 (89.33) | 83,549 (89.44) | 50,950 (89.31) | 29,732 (87.87) | 47 (94.00) | <0.0001 |
 Widowed | 28,069 (9.28) | 293 (10.17) | 27,776 (9.27) | 11,301 (9.80) | 8,360 (8.95) | 4,919 (8.62) | 3,194 (9.44) | 2 (4.00) |  |
 Separated/ Divorced | 4,573 (1.51) | 105 (3.64) | 4,468 (1.49) | 969 (0.84) | 1,458 (1.56) | 1,148 (2.01) | 892 (2.64) | 1 (2.00) |  |
 Single | 702 (0.23) | 581 (20.17) | 121 (0.04) | 27 (0.02) | 42 (0.04) | 32 (0.06) | 20 (0.06) | 0 (0.00) |  |
Household income (yuan), n (%) | |||||||||
 <5000 | 30,720 (10.16) | 348 (12.08) | 30,372 (10.14) | 15,998 (13.88) | 7,487 (8.02) | 4,035 (7.07) | 2,847 (8.41) | 5 (10.00) | <0.0001 |
 5000 – 19,999 | 148,702 (49.16) | 1,507 (52.31) | 147,195 (49.13) | 60,208 (52.23) | 42,622 (45.63) | 26,853 (47.07) | 17,487 (51.68) | 25 (50.00) |  |
 ≥20,000 | 123,088 (40.69) | 1,026 (35.61) | 122,062 (40.74) | 39,077 (33.90) | 43,300 (46.36) | 26,161 (45.86) | 13,504 (39.91) | 20 (40.00) |  |
Waist-hip ratio, mean (SD) | 0.87 (0.07) | 0.85 (0.08) | 0.87 (0.07) | 0.87 (0.07) | 0.86 (0.07) | 0.86 (0.07) | 0.87 (0.07) | 0.87 (0.07) | <0.0001 |
MET hours, n (%) | |||||||||
 <16.8 | 149,833 (49.53) | 1,683 (58.42) | 148,150 (49.44) | 53,272 (46.21) | 46,318 (49.59) | 29,983 (52.56) | 18,553 (54.83) | 24 (48.00) | <0.0001 |
 ≥16.8 | 152,677 (50.47) | 1,198 (41.58) | 151,479 (50.56) | 62,011 (53.79) | 47,091 (50.41) | 27,066 (47.44) | 15,285 (45.17) | 26 (52.00) |  |
BMI, n (%) | |||||||||
 <25 | 198,798 (65.72) | 1,989 (69.04) | 196,809 (65.68) | 77,486 (67.21) | 61,090 (65.40) | 36,615 (64.18) | 21,580 (63.77) | 38 (76.00) | <0.0001 |
 ≥25 | 103,711 (34.28) | 892 (30.96) | 102,819 (34.32) | 37,797 (32.79) | 32,319 (34.60) | 20,433 (35.82) | 12,258 (36.23) | 12 (24.00) |  |
 Missing | 1 (0.00) | 0 (0.00) | 1 (0.00) | 0 (0.00) | 0 (0.00) | 1 (0.00) | 0 (0.00) | 0 (0.00) |  |
Smoking, n (%) | |||||||||
 Smoker | 15,330 (5.07) | 189 (6.56) | 15,141 (5.05) | 5,213 (4.52) | 4,395 (4.71) | 3,008 (5.27) | 2,511 (7.42) | 14 (28.00) |  |
 Non-smoker | 287,180 (94.93) | 2,692 (93.44) | 284,488 (94.95) | 110,070 (95.48) | 89,014 (95.29) | 54,041 (94.73) | 31,327 (92.58) | 36 (72.00) | <0.0001 |
Alcohol, n (%) | |||||||||
 Alcohol drinker | 110,187 (36.42) | 1,208 (41.93) | 108,979 (36.37) | 36,279 (31.47) | 34,345 (36.77) | 23,504 (41.20) | 14,828 (43.82) | 23 (46.00) |  |
 Non-alcohol drinker | 192,323 (63.58) | 1,673 (58.07) | 190,650 (63.63) | 79,004 (68.53) | 59,064 (63.23) | 33,545 (58.80) | 19,010 (56.18) | 27 (54.00) | <0.0001 |
Gum bleed, n (%) | |||||||||
 No | 188,458 (62.30) | 1,825 (63.35) | 186,633 (62.29) | 70,790 (61.41) | 58,609 (62.74) | 35,927 (62.98) | 21,270 (62.86) | 37 (74.00) | <0.0001 |
 Yes | 114,052 (37.70) | 1,056 (36.65) | 112,996 (37.71) | 44,493 (38.59) | 34,800 (37.26) | 21,122 (37.02) | 12,568 (37.14) | 13 (26.00) |  |
Parity, n (%) | |||||||||
 0 | 4,142 (1.37) | - | 1,365 (0.46) | 104 (0.09) | 635 (0.68) | 324 (0.57) | 302 (0.89) | 0 (0.00) | <0.0001 |
 1 | 105,732 (34.95) | - | 105,637 (35.26) | 27,422 (23.79) | 37,339 (39.97) | 25,695 (45.04) | 15,163 (44.81) | 18 (36.00) |  |
 2 | 99,339 (32.84) | - | 99,330 (33.15) | 42,852 (37.17) | 29,934 (32.05) | 17,036 (29.86) | 9,494 (28.06) | 14 (28.00) |  |
 ≥3 | 93,261 | - | 93,261 (31.13) | 44,891 (38.94) | 25,487 (27.29) | 13,988 (24.52) | 8,877 (26.23) | 18 (36.00) |  |
 Missing | 36 (0.01) | - | 36 (0.01) | 14 (0.01) | 14 (0.01) | 6 (0.01) | 2 (0.01) | 0 (0.00) |  |
Pregnancy, n (%) | |||||||||
 0 | 2,881 (0.95) | - | - | - | - | - | - | - |  |
 1 | 27,386 (9.05) | - | 27,386 (9.14) | 26,765 (23.22) | 620 (0.66) | 0 (0.00) | 0 (0.00) | 1 (2.00) | <0.0001 |
 2 | 78,036 (25.80) | - | 78,036 (26.04) | 40,834 (35.43) | 36,885 (39.49) | 308 (0.54) | 0 (0.00) | 0 (0.00) |  |
 ≥3 | 194,159 (64.18) | - | 194,159 (64.80) | 47,675 (41.35) | 55,903 (59.85) | 56,741 (99.46) | 33,838 (100.00) | 2 (4.00) |  |
 Missing | 48 (0.02) | - | 48 (0.02) | 0 (0.00) | 1 (0.00) | 0 (0.00) | 0 (0.00) | 47 (94.00) |  |
Livebirths, n (%) | |||||||||
 0 | 1,214 (0.40) | - | 1,214 (0.41) | 0 (0.00) | 620 (0.66) | 307 (0.54) | 287 (0.85) | 0 (0.00) | <0.0001 |
 1 | 104,047 (34.39) | - | 104,047 (34.73) | 26,765 (23.22) | 36,885 (39.49) | 25,437 (44.59) | 14,958 (44.20) | 2 (4.00) |  |
 2 | 96,042 (31.75) | - | 96,042 (32.05) | 40,843 (35.43) | 29,036 (31.08) | 16,766 (29.39) | 9,397 (27.77) | 0 (0.00) |  |
 ≥3 | 98,279 (32.49) | - | 98,279 (32.80) | 47,675 (41.35) | 26,868 (28.76) | 14,539 (25.49) | 9,196 (27.18) | 1 (2.00) |  |
 Nulligravid | 2,881 (0.95) | - | - | - | - | - | - | - |  |
 Missing | 47 (0.02) | - | 47 (0.02) | 0 (0.00) | 0 (0.00) | 0 (0.00) | 0 (0.00) | 47 (94.00) |  |
Spontaneous abortion, n (%) | |||||||||
 0 | 272,424 (90.05) | - | 272,424 (90.92) | 115,283 (100.00) | 81,454 (87.20) | 48,584 (85.16) | 27,103 (80.10) | 0 (0.00) | <0.0001 |
 1 | 21,412 (7.08) | - | 21,412 (7.15) | 0 (0.00) | 11,955 (12.80) | 5,780 (10.13) | 3,676 (10.86) | 1 (2.00) |  |
 2 | 4,240 (1.40) | - | 4,240 (1.42) | 0 (0.00) | 0 (0.00) | 2,685 (4.71) | 1,555 (4.60) | 0 (0.00) |  |
 ≥3 | 1,504 (0.50) | - | 1,504 (0.50) | 0 (0.00) | 0 (0.00) | 0 (0.00) | 1,504 (4.44) | 0 (0.00) |  |
 Nulligravid | 2,881 (0.95) | - | - | - | - | - | - | - |  |
 Missing | 49 (0.02) | - | 49 (0.02) | 0 (0.00) | 0 (0.00) | 0 (0.00) | 0 (0.00) | 49 (98.00) |  |
Induced abortion, n (%) | |||||||||
 0 | 142,348 (47.06) | - | 142,348 (47.51) | 115,283 (100.00) | 19,135 (20.49) | 5,370 (9.41) | 2,560 (7.57) | 0 (0.00) | <0.0001 |
 1 | 83,153 (27.49) | - | 83,153 (27.75) | 0 (0.00) | 74,274 (79.51) | 7,211 (12.64) | 1,668 (4.93) | 0 (0.00) |  |
 2 | 48,160 (15.92) | - | 48,160 (16.07) | 0 (0.00) | 0 (0.00) | 44,468 (77.95) | 3,692 (10.91) | 0 (0.00) |  |
 ≥3 | 25,919 (8.57) | - | 25,919 (8.65) | 0 (0.00) | 0 (0.00) | 0 (0.00) | 25,918 (76.59) | 1 (2.00) |  |
 Nulligravid | 2,881 (0.95) | - | - | - | - | - | - | - |  |
 Missing | 49 (0.02) | - | 49 (0.02) | 0 (0.00) | 0 (0.00) | 0 (0.00) | 0 (0.00) | 49 (98.00) |  |
Stillbirth, n (%) | |||||||||
 0 | 282,538 (93.40) | - | 282,538 (94.30) | 115,283 (100.00) | 86,229 (92.31) | 51,914 (91.00) | 29,112 (86.03) | 0 (0.00) | <0.0001 |
 1 | 13,174 (4.35) | - | 13,174 (4.40) | 0 (0.00) | 7,180 (7.69) | 3,469 (6.08) | 2,525 (7.46) | 0 (0.00) |  |
 2 | 2,762 (0.91) | - | 2,762 (0.92) | 0 (0.00) | 0 (0.00) | 1,666 (2.92) | 1,096 (3.24) | 0 (0.00) |  |
 ≥3 | 1,105 (0.37) | - | 1,105 (0.37) | 0 (0.00) | 0 (0.00) | 0 (0.00) | 1,105 (3.27) | 0 (0.00) |  |
 Nulligravid | 2,881 (0.95) | - |  | - | - | - | - | - |  |
 Missing | 50 (0.02) | - | 50 (0.02) | 0 (0.00) | 0 (0.00) | 0 (0.00) | 0 (0.00) | 50 (100.00) |  |