Table 5 Adjusted relative risks of cholecystectomy according to crude waist circumferences among US women in the Nurses' Health Study.

	Crude waist circumference category (inches)
	<26	26–<28	28–<30	30–<32	32–<36	⩾36	p for trend
Cases	163	392	589	605	880	568	–
Person years	51 439	104 552	121 003	89 504	99 317	48 469	–
Model 1: age adjusted (RR)	1.00	1.31 (1.00–1.70)	1.37 (1.05–1.80)	1.56 (1.21–2.03)	1.79 (1.39–2.31)	2.63 (2.06–3.35)	<0.0001
Model 2: multivariable (RR)	1.00	1.14 (0.95–1.37)	1.47 (1.24–1.75)	1.99 (1.67–2.37)	2.61 (2.20–3.09)	3.40 (2.84–4.07)	<0.0001
Model 3: multivariable (RR)	1.00	1.13 (0.94–1.36)	1.44 (1.21–1.72)	1.92 (1.61–2.29)	2.48 (2.09–2.94)	3.12 (2.60–3.74)	<0.0001
Model 4: multivariable (RR)	1.00	1.09 (0.91–1.31)	1.27 (1.06–1.52)	1.51 (1.25–1.82)	1.68 (1.38–2.03)	1.72 (1.39–2.13)	<0.0001

RR, relative risk (95% confidence interval).

For explanation of models 1–4, see footnote to table 3.