Baseline demographic and clinical characteristics for the 4 cohorts within the subsample of patients with inflammatory polyarthritis referred by their general practitioner.
| Characteristics | Cohort 1, 1990–1994, n = 533 | Cohort 2, 1995–1999, n = 367 | Cohort 3, 2000–2004, n = 149 | Cohort 4, 2005–2008, n = 87 | p | ||||
|---|---|---|---|---|---|---|---|---|---|
| Demographics | |||||||||
| Age at symptom onset, yrs, median [IQR] | 533/533 | 53 [41, 65] | 367/367 | 44 [45, 65] | 149/149 | 56 [42, 67] | 87/87 | 58 [50, 70] | 0.03* |
| Symptom duration (mos), median [IQR] | 533/533 | 4 [2, 7] | 367/367 | 5 [3, 9] | 149/149 | 6 [3, 9] | 87/87 | 5 [2, 9] | < 0.001* |
| Sex, female, % | 356/533 | 66.8 | 255/367 | 69.4 | 108/149 | 73.1 | 61/87 | 70.0 | 0.56 |
| Smoking status, % | |||||||||
| Never | 169/532 | 31.8 | 159/366 | 43.4 | 44/137 | 32.1 | 24/80 | 30.0 | < 0.001* |
| Ex-smoker | 217/532 | 40.8 | 124/366 | 33.9 | 63/147 | 46.0 | 40/80 | 50.0 | 0.06* |
| Current smoker | 146/532 | 27.4 | 83/366 | 22.7 | 30/137 | 22.0 | 16/80 | 20.0 | 0.09 |
| BMI | |||||||||
| Normal, < 25 | NA† | NA† | 55/143 | 38.4 | 22/85 | 25.9 | 0.07 | ||
| Overweight, ≥ 25 and < 30, | 60/143 | 42.0 | 33/85 | 38.8 | 0.72 | ||||
| Obese, ≥ 30 and < 35 | 20/143 | 14.0 | 23/85 | 27.1 | 0.01* | ||||
| Morbidly obese, ≥ 35 | 8/143 | 5.6 | 7/85 | 8.2 | 0.42 | ||||
| Disease characteristics | |||||||||
| DAS28, mean (SD) | 429/533 | 3.78 (1.43) | 296/367 | 3.69 (1.48) | 118/149 | 3.51 (1.21) | 75/87 | 3.58 (1.10) | 0.24 |
| HAQ score, median [IQR] | 530/533 | 0.63 [0.13, 1.13] | 366/367 | 0.63 [0.13, 1.13] | 143/149 | 0.75 [0.25, 1.25] | 87/87 | 0.75 [0.38, 1.25] | 0.24 |
| RF and/or anti-CCP positivity, % | 112/402 | 27.9 | 89/302 | 29.5 | 43/119 | 36.1 | 35/75 | 46.7 | 0.007* |
| CRP, mg/l, median [IQR] | 429/533 | 4 [0, 14] | 296/367 | 7 [0, 19] | 118/149 | 6 [2, 19] | 75/87 | 12 [7, 20] | < 0.001* |
| Met 2010 RA criteria, % | 293/533 | 55.0 | 169/321 | 46.1 | 69/149 | 46.3 | 40/87 | 46.0 | < 0.001* |
| Medication | |||||||||
| Used DMARD prior to assessment, % | 30/533 | 5.6 | 46/367 | 12.5 | 28/149 | 18.8 | 12/87 | 13.8 | < 0.001* |
| Used methotrexate prior to assessment, % | 1/533 | 0.2 | 15/367 | 4.1 | 11/149 | 7.4 | 7/87 | 8.1 | < 0.001* |
| Used steroids prior to assessment, % | 19/533 | 3.6 | 29/367 | 7.9 | 25/149 | 16.8 | 12/87 | 13.8 | < 0.001* |
↵* Statistical significance set at 0.05 level.
↵† NA: Not available because these data were not collected. HAQ: Health Assessment Questionnaire; DAS28: Disease Activity Score; RF: rheumatoid factor; anti-CCP: anticyclic citrullinated peptide antibody; DMARD: disease-modifying antirheumatic drugs; IQR: interquartile range; BMI: body mass index; CRP: C-reactive protein; RA: rheumatoid arthritis