Table 1.
Selected baseline characteristics of study population.
| Variable | Total (N = 1,357,736) | Women not diagnosed with seropositive RA (N = 1,351,680) | Women diagnosed with seropositive RA (N = 6,056) | OR (95% CI) | p-value |
|---|---|---|---|---|---|
| Mean age, y (SD) | 61.4 (8.3) | 61.4 (8.3) | 60.7 (7.6) | 0.99 (0.99–0.99) | < 0.001 |
| Age at menarche, N (%) | |||||
| Mean (SD) | 16.5 (1.8) | 16.5 (1.8) | 16.5 (1.9) | 1.01 (0.99–1.02) | 0.332 |
| ≤ 15 years | 422,281 (31.1) | 420,445 (31.1) | 1836 (30.3) | 1 (ref.) | 0.474 |
| 16 years | 287,920 (21.2) | 286,618 (21.2) | 1302 (21.5) | 1.04 (0.97–1.12) | |
| 17 years | 269,426 (19.8) | 268,189 (19.8) | 1237 (20.4) | 1.06 (0.98–1.14) | |
| ≥ 18 years | 378,109 (27.9) | 376,428 (27.9) | 1681 (27.8) | 1.02 (0.96–1.09) | |
| Age at menopause, N (%) | |||||
| Mean (SD) | 50.0 (4.0) | 50.0 (4.0) | 50.0 (4.0) | 1.00 (0.99–1.00) | 0.499 |
| < 40 years | 23,170 (1.7) | 23,064 (1.7) | 106 (1.8) | 1 (ref.) | 0.588 |
| 40–44 years | 77,503 (5.7) | 77,131 (5.7) | 372 (6.1) | 1.05 (0.85–1.30) | |
| 45–49 years | 369,193 (27.2) | 367,536 (27.2) | 1657 (27.4) | 0.98 (0.81–1.19) | |
| 50–54 years | 743,286 (54.7) | 740,016 (54.8) | 3270 (54.0) | 0.96 (0.79–1.17) | |
| ≥ 55 years | 144,584 (10.7) | 143,933 (10.7) | 651 (10.8) | 0.98 (0.80–1.21) | |
| Reproductive period, N (%) | |||||
| Mean (SD) | 33.6 (4.4) | 33.6 (4.4) | 33.5 (4.4) | 1.00 (0.99–1.00) | 0.307 |
| < 30 years | 186,341 (13.7) | 185,493 (13.7) | 848 (14) | 1 (ref.) | 0.660 |
| 30–34 years | 567,444 (41.8) | 564,895 (41.8) | 2549 (42.1) | 0.99 (0.91–1.07) | |
| 35–39 years | 517,205 (38.1) | 514,913 (38.1) | 2292 (37.9) | 0.97 (0.90–1.05) | |
| ≥ 40 | 86,746 (6.4) | 86,379 (6.4) | 367 (6.1) | 0.93 (0.82–1.05) | |
| Parity, N (%) | |||||
| Nulliparous | 33,605 (2.5) | 33,429 (2.5) | 176 (2.9) | 1 (ref.) | 0.084 |
| 1 child | 82,685 (6.1) | 82,308 (6.1) | 377 (6.2) | 0.87 (0.73–1.04) | |
| ≥ 2 children | 1,241,446 (91.4) | 1,235,943 (91.4) | 5503 (90.9) | 0.85 (0.73–0.98) | |
| Duration of breastfeeding, N (%) | |||||
| Never | 90,070 (6.6) | 89,617 (6.6) | 453 (7.5) | 1 (ref.) | 0.026 |
| < 0.5 years | 89,470 (6.6) | 89,089 (6.6) | 381 (6.3) | 0.85 (0.74–0.97) | |
| 0.5 to < 1 years | 237,224 (17.5) | 236,135 (17.5) | 1089 (18.0) | 0.91 (0.82–1.02) | |
| ≥ 1 years | 940,972 (69.3) | 936,839 (69.3) | 4133 (68.3) | 0.87 (0.79–0.96) | |
| Oral contraceptive use, No. (%) | |||||
| Never used | 1,084,881 (79.9) | 1,080,038 (79.9) | 4843 (80.0) | 1 (ref.) | 0.477 |
| < 1 years | 123,156 (9.07) | 122,584 (9.1) | 572 (9.5) | 1.04 (0.95–1.14) | |
| ≥ 1 years | 82,398 (6.07) | 82,054 (6.1) | 344 (5.7) | 0.94 (0.84–1.04) | |
| Unknown | 67,301 (4.96) | 67,004 (5.0) | 297 (4.9) | 0.99 (0.88–1.11) | |
| Hormone therapy, N (%) | |||||
| Never used | 1,097,847 (80.9) | 1,093,086 (80.9) | 4761 (78.6) | 1 (ref.) | < 0.001 |
| < 2 years | 123,195 (9.1) | 122,583 (9.1) | 612 (10.1) | 1.15 (1.05–1.25) | |
| 2 to < 5 years | 50,640 (3.7) | 50,381 (3.7) | 259 (4.3) | 1.18 (1.04–1.34) | |
| ≥ 5 years | 38,797 (2.9) | 38,583 (2.9) | 214 (3.5) | 1.27 (1.11–1.46) | |
| Unknown | 47,257 (3.5) | 47,047 (3.5) | 210 (3.5) | 1.03 (0.89–1.18) | |
| Smoking history, N (%) | |||||
| Never smoker | 1,306,285 (96.2) | 1,300,499 (96.2) | 5786 (95.5) | 1 (ref.) | 0.024 |
| Former smoker | 14,512 (1.1) | 14,437 (1.1) | 75 (1.2) | 1.17 (0.93–1.47) | |
| Current smoker | 36,939 (2.7) | 36,744 (2.7) | 195 (3.2) | 1.19 (1.03–1.38) | |
| Alcohol consumption, N (%) | |||||
| Non | 1,186,714 (87.4) | 1,181,322 (87.4) | 5,392 (89.0) | 1 (ref.) | 0.001 |
| Mild (< 30 g/day) | 163,966 (12.1) | 163,328 (12.1) | 638 (10.5) | 0.86 (0.79–0.93) | |
| Heavy (≥ 30 g/day) | 7056 (0.5) | 7030 (0.5) | 26 (0.4) | 0.81 (0.55–1.19) | |
| Regular physical activity | 251,179 (18.5) | 250,138 (18.5) | 1041 (17.2) | 0.91 (0.86–0.98) | 0.009 |
| Anthropometrics | |||||
| Body mass index, N (%) | |||||
| < 18.5 kg/m2 | 28,840 (2.1) | 28,670 (2.1) | 170 (2.8) | 1.25 (1.07–1.56) | < 0.001 |
| 18.5 to < 23 kg/m2 | 469,107 (34.6) | 466,886 (34.5) | 2221 (36.7) | 1 (ref.) | |
| 23 to < 25 kg/m2 | 360,783 (26.6) | 359,175 (26.6) | 1608 (26.6) | 0.94 (0.88–1.00) | |
| 25 to < 30 kg/m2 | 443,423 (32.7) | 441,593 (32.7) | 1830 (30.2) | 0.87 (0.82–0.93) | |
| ≥ 30 kg/m2 | 55,583 (4.1) | 55,356 (4.1) | 227 (3.8) | 0.86 (0.75–0.99) | |
| Systolic BP (mmHg) | 125.6 ± 16.2 | 125.6 ± 16.2 | 124.3 ± 15.8 | 1.00 (0.99–1.00) | < 0.001 |
| Diastolic BP (mmHg) | 76.9 ± 10.2 | 76.9 ± 10.2 | 76.4 ± 10.1 | 1.00 (0.99–1.00) | < 0.001 |
| Laboratory findings | |||||
| Glucose (mg/dL) | 99.7 ± 24.2 | 99.7 ± 24.3 | 96.9 ± 21.5 | 0.99 (0.99–1.00) | < 0.001 |
| Cholesterol (mg/dL) | 208.3 ± 43.9 | 208.3 ± 43.8 | 205.2 ± 52.3 | 1.00 (1.00–1.00) | < 0.001 |
| Comorbidity | |||||
| Hypertension, N (%) | 574,745 (42.33) | 572,398 (42.4) | 2347 (38.8) | 0.86 (0.82–0.91) | < 0.001 |
| Diabetes mellitus, N (%) | 174,870 (12.88) | 174,248 (12.9) | 622 (10.3) | 0.77 (0.71–0.84) | < 0.001 |
| Dyslipidemia, N (%) | 462,410 (34.06) | 460,547 (34.1) | 1,863 (30.8) | 0.86 (0.81–0.91) | < 0.001 |
| Cancer, N (%) | 36, 317 (2.7) | 36,193 (2.7) | 124 (2.1) | 0.76 (0.64–0.91) | 0.002 |
| Income | |||||
| Q1 (lowest) | 309,432 (22.8) | 308,044 (22.8) | 1388 (22.9) | 1 (ref.) | 0.873 |
| Q2 | 252,891 (18.6) | 251,759 (18.6) | 1132 (18.7) | 1.00 (0.92–1.08) | |
| Q3 | 335,670 (24.7) | 334,155 (24.7) | 1515 (25.0) | 1.01 (0.94–1.08) | |
| Q4 (highest) | 459,743 (33.9) | 457,722 (33.9) | 2021 (33.4) | 0.98 (0.92–1.05) | |
OR odds ratio, 95% CI 95% confidence interval, SD standard deviation, BP blood pressure.