HRs for incident RA, and incident seropositive or seronegative RA phenotypes, according to cumulative average Body Mass Index (BMI) in Nurses’ Health Study and Nurses’ Health Study II
| Cumulative average BMI | Nurses’ Health Study | Nurses’ Health Study II | Pooled HR (95% CI) | p Het† | ||||
|---|---|---|---|---|---|---|---|---|
| Number of cases/person-years | Age-adjusted HR (95% CI) | Multivariable HR (95% CI)* | Number of cases/ person-years | Age-adjusted HR (95% CI) | Multivariable HR (95% CI)* | |||
| All RA cases | ||||||||
| All RA | ||||||||
| 8.5–24.9 | 471/1 708 379 | 1.00 | 1.00 | 168/1 175 594 | 1.00 | 1.00 | 1.00 | |
| 25.0–29.9 | 247/741 443 | 1.15 (0.99 to 1.35) | 1.17 (1.00 to 1.37) | 103/454 650 | 1.47 (1.15 to 1.88) | 1.38 (1.08 to 1.77) | 1.23 (1.06 to 144) | 0.271 |
| ≥30.0 | 108/315 373 | 1.18 (0.96 to 1.46) | 1.21 (0.97 to 1.50) | 84/304 274 | 1.73 (1.33 to 2.25) | 1.53 (1.16 to 2.01) | 1.34 (1.06 to 1.68) | 0.183 |
| p trend | 0.052 | 0.034 | <0.001 | 0.001 | <0.001 | |||
| Seropositive RA | ||||||||
| 18.5–24.9 | 289/1 596 366 | 1.00 | 1.00 | 105/1 152 762 | 1.00 | 1.00 | 1.00 | |
| 25.0–29.9 | 157/683 973 | 1.24 (1.02 to 1.51) | 1.25 (1.02 to 1.52) | 69/443 759 | 1.59 (1.17 to 2.16) | 1.52 (1.11 to 2.06) | 1.32 (1.11 to 1.58) | 0.296 |
| ≥30.0 | 64/288 011 | 1.20 (0.91 to 1.57) | 1.21 (0.92 to 1.60) | 58/294 997 | 1.92 (1.39 to 2.66) | 1.75 (1.25 to 2.45) | 1.44 (1.00 to 2.06) | 0.100 |
| p trend | 0.062 | 0.058 | <0.001 | <0.001 | 0.004 | |||
| Seronegative RA | ||||||||
| 18.5–24.9 | 182/1 701 227 | 1.00 | 1.00 | 63/1 173 261 | 1.00 | 1.00 | 1.00 | |
| 25.0–29.9 | 90/738 623 | 1.06 (0.82 to 1.37) | 1.09 (0.84 to 1.41) | 34/453 555 | 1.29 (0.85 to 1.96) | 1.19 (0.78 to 1.81) | 1.11 (0.89 to 1.39) | 0.729 |
| ≥30.0 | 44/314 252 | 1.21 (0.87 to 1.69) | 1.25 (0.89 to 1.76) | 26/303 378 | 1.43 (0.90 to 2.27) | 1.20 (0.75 to 1.93) | 1.23 (0.94 to 1.63) | 0.888 |
| p trend | 0.263 | 0.191 | 0.104 | 0.411 | 0.125 | |||
| RA onset ≤55 years of age | ||||||||
| All RA | ||||||||
| 18.5–24.9 | 196/882 579 | 1.00 | 1.00 | 147/1 125 955 | 1.00 | 1.00 | 1.00 | |
| 25.0–29.9 | 74/282 849 | 1.12 (0.86 to 1.47) | 1.12 (0.86 to 1.47) | 88/423 641 | 1.51 (1.16 to 1.97) | 1.41 (1.08 to 1.84) | 1.26 (1.01.1.57) | 0.244 |
| ≥30.0 | 42/121 301 | 1.46 (1.04 to 2.04) | 1.44 (1.02 to 2.03) | 71/280 790 | 1.79 (1.34 to 2.38) | 1.56 (1.16 to 2.09) | 1.51 (1.20 to 1.88) | 0.727 |
| p trend | 0.031 | 0.039 | <0.001 | 0.002 | <0.001 | |||
| Seropositive RA | ||||||||
| 18.5–24.9 | 126/814 611 | 1.00 | 1.00 | 92/1 103 419 | 1.00 | 1.00 | 1.00 | |
| 25.0–29.9 | 47/254 650 | 1.15 (0.82 to 1.60) | 1.13 (0.80 to 1.59) | 58/412 959 | 1.61 (1.15 to 2.23) | 1.52 (1.09 to 2.12) | 1.31 (0.98 to 1.75) | 0.226 |
| ≥30.0 | 27/107 504 | 1.51 (0.99 to 2.29) | 1.48 (0.97.2.28) | 48/271 727 | 1.95 (1.37 to 2.78) | 1.75 (1.22 to 2.52) | 1.63 (1.24 to 2.16) | 0.564 |
| p trend | 0.056 | 0.074 | <0.001 | 0.002 | <0.001 | |||
| Seronegative RA | ||||||||
| 18.5–24.9 | 70/877 769 | 1.00 | 1.00 | 55/1 123 656 | 1.00 | 1.00 | 1.00 | |
| 25.0–29.9 | 27/281 358 | 1.14 (0.73 to 1.78) | 1.16 (0.73 to 1.82) | 30/422 569 | 1.37 (0.87 to 2.14) | 1.26 (0.80 to 1.98) | 1.21 (0.88 to 1.66) | 0.793 |
| ≥30.0 | 15/120 604 | 1.48 (0.84 to 2.59) | 1.48 (0.83 to 2.63) | 23/279 920 | 1.54 (0.95 to 2.52) | 1.28 (0.77 to 2.12) | 1.36 (0.93 to 1.99) | 0.709 |
| p trend | 0.173 | 0.174 | 0.065 | 0.299 | 0.100 | |||
Bold typeface indicates significant results.
*Adjusted for age, community median income, smoking (pack-years), alcohol use (<5.0, 5.0-<15.0, ≥15 g/day) and physical activity (0–3, 3–9, 9–18, 18–27, ≥27 METs/week).
†p Value for test of heterogeneity (het) between the 2 cohorts. Risk estimates were pooled by using a DerSimonian and Laird random-effects model.
MET, metabolic equivalent; RA, rheumatoid arthritis.