Table 6 Multivariable relative risks of cholecystectomy stratified by selected risk factors according to adjusted waist circumference among US women in the Nurses' Health Study*.

Variable	Height adjusted waist circumference category (inches)
	<26	26–<28	28–<30	30–<32	32–<36	⩾36	p for trend
Age
⩽60 y	1.0	1.24	1.38	1.58	1.87	2.03	<0.0001
>60 y	1.0	1.25	1.56	1.80	2.05	1.92	0.0005
Recent weight change†
Stable	1.0	1.25	1.66	2.14	2.94	3.86	<0.0001
Gained 4 lbs	1.0	0.86	0.99	1.04	1.48	1.82	<0.0001
Lost 4 lbs	1.0	3.45	2.71	5.26	4.87	5.80	0.0002
Current smoking
No	1.0	1.24	1.45	1.66	1.94	1.92	<0.0001
Yes	1.0	1.29	1.34	1.59	1.81	2.18	0.007
Physical activity‡
Low	1.0	1.13	1.33	1.66	2.01	2.22	<0.0001
High	1.0	1.29	1.52	1.69	1.94	1.84	<0.0001
Current alcohol use
No	1.0	1.29	1.54	1.59	1.94	2.00	<0.0001
Yes	1.0	1.27	1.49	1.82	1.99	1.93	<0.0001
Hormone replacement therapy
Premenopausal	1.0	1.42	1.72	1.75	1.98	1.81	0.07
Never	1.0	1.18	1.17	1.78	2.14	2.08	0.0008
Current	1.0	1.11	1.37	1.60	1.85	1.71	<0.0001
Past	1.0	1.89	2.38	2.41	2.85	3.29	0.01
Coffee intake
No	1.0	1.39	1.51	1.76	2.10	1.91	0.001
Yes	1.0	1.18	1.45	1.64	1.87	2.03	<0.0001
Dietary fibre intake†
Low	1.0	1.24	1.43	1.51	1.90	2.29	<0.0001
High	1.0	1.29	1.51	1.75	1.97	1.84	<0.0001

*The multivariable model included the same covariates as in model 2 in tables 3–5. The variable used for stratification was excluded from the model.

†Recent weight change was defined as weight change in the previous two years.

‡Median values were used as the cut off points for stratification.