Table 1.
Baseline characteristics of individuals in the incident OA cohorts and their matched non-OA cohorts
| Knee OA (n=20 696) |
Non-OA (n=81 137) |
SDs | Hip OA (n=10 411) |
Non-OA (n=41 594) |
SDs | Hand OA (n=6329) |
Non-OA (n=25 206) |
SDs | |
| Age*, mean (SD), years | 66.2 (9.6) | 66.1 (9.5) | 0.010 | 66.9 (9.2) | 66.8 (9.1) | 0.011 | 64.2 (8.7) | 64.0 (8.7) | 0.017 |
| Female*†, % | 51.5 | 51.1 | 0.010 | 54.7 | 54.6 | 0.003 | 68.2 | 68.6 | 0.009 |
| BMI*, mean (SD) | 28.2 (4.6) | 27.9 (4.3) | 0.071 | 26.9 (4.3) | 26.7 (4.0) | 0.041 | 26.3 (4.3) | 26.1 (4.0) | 0.038 |
| Region*, % | 0.124 | 0.070 | 0.113 | ||||||
| England | 72.81 | 68.00 | 70.33 | 67.85 | 72.12 | 68.39 | |||
| Northern Ireland | 1.93 | 3.34 | 2.82 | 3.51 | 2.86 | 3.33 | |||
| Scotland | 15.24 | 16.95 | 17.46 | 17.64 | 16.42 | 16.49 | |||
| Wales | 10.02 | 11.71 | 9.39 | 11.00 | 8.60 | 11.79 | |||
| Smoking status*, % | 0.080 | 0.055 | 0.094 | ||||||
| Non-smoker | 56.99 | 55.24 | 56.00 | 55.78 | 58.04 | 57.80 | |||
| Ex-smoker | 30.39 | 29.37 | 29.87 | 28.34 | 28.69 | 25.96 | |||
| Current smoker | 11.64 | 14.30 | 13.03 | 14.79 | 12.45 | 15.37 | |||
| Missing | 0.98 | 1.09 | 1.10 | 1.09 | 0.82 | 0.87 | |||
| Alcohol drinking*, % | 0.029 | 0.072 | 0.067 | ||||||
| Non-drinker | 14.99 | 15.33 | 13.40 | 15.62 | 13.64 | 15.61 | |||
| Ex-drinker | 1.96 | 1.95 | 1.83 | 1.83 | 1.80 | 1.63 | |||
| Current drinker | 77.78 | 76.84 | 79.67 | 76.83 | 79.82 | 77.34 | |||
| Missing | 5.27 | 5.88 | 5.10 | 5.72 | 4.74 | 5.42 | |||
| Medication‡, % | |||||||||
| Aspirin | 19.08 | 20.56 | 0.037 | 19.41 | 20.49 | 0.027 | 13.83 | 15.22 | 0.040 |
| Glucocorticoids | 5.03 | 5.10 | 0.004 | 5.55 | 5.17 | 0.017 | 5.10 | 5.13 | 0.001 |
| Hormone replacement therapy | 6.25 | 5.62 | 0.027 | 6.35 | 6.32 | 0.001 | 12.15 | 9.67 | 0.080 |
| Anticoagulation | 3.73 | 3.19 | 0.029 | 3.48 | 3.21 | 0.015 | 2.21 | 2.27 | 0.004 |
| Comorbidity‡§, % | |||||||||
| Cancer | 9.76 | 9.84 | 0.003 | 10.00 | 10.33 | 0.011 | 9.92 | 9.20 | 0.024 |
| Congestive heart failure | 2.26 | 2.34 | 0.006 | 2.05 | 2.32 | 0.019 | 1.60 | 1.52 | 0.006 |
| Stroke | 2.63 | 3.01 | 0.023 | 2.49 | 3.12 | 0.038 | 1.96 | 2.34 | 0.026 |
| Myocardial infarction | 4.27 | 5.16 | 0.042 | 4.76 | 5.25 | 0.022 | 3.18 | 3.61 | 0.024 |
| Atrial fibrillation | 5.05 | 4.50 | 0.026 | 4.74 | 4.52 | 0.010 | 3.37 | 3.15 | 0.012 |
| Hypertension | 44.58 | 44.98 | 0.008 | 42.33 | 43.60 | 0.026 | 35.06 | 37.11 | 0.043 |
| Diabetes mellitus | 11.03 | 13.81 | 0.084 | 10.95 | 12.55 | 0.050 | 9.34 | 9.64 | 0.010 |
| Chronic obstructive pulmonary disease | 3.39 | 4.15 | 0.040 | 3.76 | 4.37 | 0.031 | 3.29 | 3.74 | 0.024 |
| Systemic lupus erythematosus | 0.06 | 0.07 | 0.004 | 0.07 | 0.07 | 0.001 | 0.03 | 0.13 | 0.036 |
| Rheumatoid arthritis | 0.68 | 0.69 | 0.001 | 0.71 | 0.71 | <0.001 | 0.51 | 0.62 | 0.016 |
| Chronic kidney disease | 6.90 | 6.72 | 0.007 | 6.87 | 6.70 | 0.007 | 5.10 | 5.30 | 0.009 |
| Inflammatory bowel disease | 1.18 | 1.08 | 0.010 | 1.16 | 1.12 | 0.004 | 1.33 | 1.09 | 0.022 |
| Varicose veins | 10.46 | 8.03 | 0.084 | 10.39 | 8.09 | 0.080 | 10.6 | 8.75 | 0.063 |
| Coagulation disturbances | 0.01 | 0.01 | <0.001 | 0.00 | 0.00 | 0.007 | 0.00 | 0.02 | 0.020 |
| Trauma¶ | 0.04 | 0.04 | <0.001 | 0.05 | 0.03 | 0.010 | 0.06 | 0.04 | 0.008 |
| Fracture¶ | 1.11 | 1.02 | 0.009 | 1.00 | 1.03 | 0.003 | 1.36 | 1.09 | 0.025 |
| Surgery¶, % | 2.74 | 2.52 | 0.014 | 2.75 | 2.63 | 0.007 | 2.45 | 2.26 | 0.012 |
| Hospitalisation¶, % | 13.41 | 11.28 | 0.065 | 11.52 | 11.32 | 0.006 | 12.36 | 11.49 | 0.027 |
| GP visits¶, mean (SD) | 4.0 (3.1) | 3.7 (3.0) | 0.120 | 4.1 (3.2) | 3.6 (3.0) | 0.154 | 3.9 (3.1) | 3.6 (2.9) | 0.117 |
*Sociodemographic and anthropometric characteristics (age, sex, BMI and region) and lifestyle factors (smoking status and alcohol drinking) were assessed using the nearest available data prior to the index date.
†Before age, sex, entry time and BMI matching, the female ratios were 54.7% in knee OA cohort and 51.7% in its comparative non-OA cohort; 57.2% in hip OA cohort and 51.7% in its comparative non-OA cohort; and 67.2% in hand OA cohort and 51.7% in its comparative non-OA cohort.
‡Comorbidities were assessed at any time and all medication use was assessed within 1 year before the index date.
§We defined the presence of comorbidities using Read codes as recorded by GPs.
¶The occurrence of trauma, fracture, surgery and hospitalisation, as well as the number of GP visits, were ascertained in the year prior to the index date.
BMI, body mass index; GP, general practitioner; OA, osteoarthritis; SDs, standardised differences.