Table 4 Adjusted relative risks of cholecystectomy according to height adjusted waist circumferences among US women in the Nurses' Health Study.

	Height adjusted waist circumference category (inches)
	<26	26–<28	28–<30	30–<32	32–<36	⩾36	p for trend
Cases	103	367	584	598	928	617	–
Person years	37 283	100 866	122 802	94 163	105 545	53 624	–
Model 1: age adjusted (RR)	1.00	1.16 (0.96–1.39)	1.48 (1.24–1.76)	2.03 (1.70–2.41)	2.61 (2.20–3.09)	3.52 (2.95–4.20)	<0.0001
Model 2: multivariable (RR)	1.00	1.29 (1.03–1.60)	1.65 (1.34–2.04)	2.18 (1.73–2.69)	2.99 (2.43–3.68)	3.87 (3.12–4.79)	<0.0001
Model 3: multivariable (RR)	1.00	1.28 (1.03–1.59)	1.62 (1.31–2.01)	2.11 (1.70–2.61)	2.84 (2.31–3.50)	3.55 (2.86–4.41)	<0.0001
Model 4: multivariable (RR)	1.00	1.25 (1.00–1.56)	1.46 (1.17–1.82)	1.69 (1.35–2.11)	1.95 (1.56–2.45)	1.96 (1.53–2.51)	<0.0001

RR, relative risk (95% confidence interval).

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