Table 4. Relative risks of environmental variables for Type 2 Diabetes, Crohn's disease and Rheumatoid Arthritis.

Disease	Environmental Variable	Level	Proportion in the population	Relative risk
		<23	0.20	1.00
		23–23.9	0.16	1.00
		24–24.9	0.14	1.50
		25–26.9	0.27	2.20
Type 2 Diabetes	Body Mass Index	27–28.9	0.14	4.40
		29–30.9	0.06	6.70
		31–32.9	0.02	11.6
		33–34.9	0.01	21.3
		> = 35	0.01	42.1
		Never Smoked	0.50	1.00
	Smoking	Ex-Smoker	0.39	1.10
		<20 cigs/day	0.04	1.50
		> = 20 cigs/day	0.07	1.70
		Never Smoked	0.545	1.00
Crohn's Disease	Smoking	Ex-Smoker	0.245	1.70
		Current-Smoker	0.198	3.00
		Never Smoked	0.498	1.00
Rheumatoid Arthritis	Smoking	Ex-Smoker	0.276	1.40
		Current-Smoker	0.227	1.30