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.