TABLE 4.

Joint association of body mass index (BMI) and abdominal adiposity measures with COPD risk

	BMI kg·m−2				p-value for interaction
	<18.5	18.5–<24.0	24.0–<28.0	≥28.0
Waist circumference cm					0.703
<85 (male) <80 (female)	1.77 (1.66–1.89)	1.00	0.87 (0.80–0.95)	1.04 (0.59–1.83)
85–<90 (male) 80–<85 (female)	1.91 (0.85–4.25)	1.08 (1.00–1.17)	0.95 (0.88–1.02)	1.18 (0.92–1.50)
≥90 (male) ≥85 (female)	2.14 (0.53–8.57)	1.09 (0.95–1.26)	1.08 (1.01–1.15)	1.12 (1.04–1.21)
Waist-to-hip ratio					0.017
<0.9 (male) <0.8 (female)	1.87 (1.72–2.02)	1.00	0.81 (0.70–0.94)	0.78 (0.46–1.32)
0.9–<0.95 (male) 0.8–<0.85 (female)	1.75 (1.51–2.01)	1.01 (0.94–1.08)	0.90 (0.82–0.99)	1.01 (0.81–1.26)
≥0.95 (male) ≥0.85 (female)	1.58 (1.30–1.93)	1.09 (1.02–1.17)	1.06 (0.99–1.13)	1.17 (1.07–1.28)
Waist-to-height ratio					0.462
<0.5	1.79 (1.67–1.92)	1.00	0.87 (0.76–0.99)	0.40 (0.06–2.84)
≥0.5	1.78 (1.18–2.69)	1.07 (1.01–1.13)	1.01 (0.96–1.06)	1.13 (1.05–1.22)

Data are presented as hazard ratio (95% CI), unless otherwise stated. Hazard ratios were estimated by joint categorisation of BMI and each measure of abdominal adiposity (waist circumference, waist-to-hip ratio and waist-to-height ratio). Covariate adjustment was based on model 2. p-values for interaction were calculated by likelihood ratio test comparing models with and without a product term of BMI and abdominal adiposity measures.