Table 4

Adjusted^4-150 relative risk (with 95% confidence interval (CI)) of developing rheumatoid factor positive rheumatoid arthritis for different factors

Factor	Unit or category	Number of subjects examined	Number of incident cases	Relative risk	95% CI	p Value^4-151
Consumption of coffee		⩽3 Cups/day	4 641	10	1.00
Consumption of coffee		⩾4 Cups/day	14 340	79	2.20	1.13 to 4.27	0.01
Age	For each SD, 15.4 years	18 981	89	1.20	0.91 to 1.59	0.19
Body mass index	For each SD, 4.1 kg/m²	6 809	69	1.11	0.89 to 1.37	0.36
Serum cholesterol	For each SD, 1.4 mmol/l	18 981	89	1.00	0.79 to 1.26	0.99
Sex		Men	9 705	31	1.00
Sex		Women	9 276	58	2.58	1.48 to 4.50	0.0007
Level of education		0–8 years	12 435	64	1.00
		9–12 years	5 368	19	0.77	0.45 to 1.32	0.56
		⩾13 years	1 178	6	1.14	0.48 to 2.68
Smoking		Never smoked	10 067	46	1.00
		Quit	3 411	16	1.76	0.92 to 3.38
		Cigars, pipe or					0.14
		⩽14 Cigarettes/day	2 718	11	1.28	0.63 to 2.57
		15–24 Cigarettes/day	2 252	12	2.28	1.07 to 4.85
		⩾25 Cigarettes/day	533	4	3.43	1.10 to 10.70
Intake of alcohol		Not at all	8 026	40	1.00
		1–99 grams/month	3 383	18	1.15	0.64 to 2.05
		100–499 grams/month	5 180	22	1.09	0.59 to 2.10	0.97
		⩾500 grams/month	2 392	9	1.04	0.44 to 2.50

↵4-150 All variables in the table were included in the Cox model.
↵4-151 Likelihood ratio test for linear trend (continuous variables) or for heterogeneity (groups of categorised variables).