Table 4.

Segmented multivariate stepwise regression analysis (dependent variable: arousal index (ArI))

	Stage I: AHI<10 (N=848)			Stage II: 10<AHI<30 (N=695)			Stage III: 30<AHI<55 (N=633)			Stage IV: AHI>55 (N=807)
Variables	β	95% CI	p Value	β	95% CI	p Value	β	95% CI	p Value	β	95% CI	p Value
Sex	−4.200	−6.539 to −1.861	<0.001	−5.076	−8.815 to −1.337	0.008	–	–	–	−8.377	−15.873 to −0.881	0.029
BMI	–	–	–	–	–	–	–	–	–	−0.804	−1.401 to −0.206	0.008
IR	3.424	1.630 to 5.218	<0.001	–	–	–	–	–	–	9.103	5.511 to 12.694	<0.001
ESS	–	–	–	–	–	–	–	–	–	0.629	0.286 to 0.971	<0.001
ApoE	–	–	–	−2.037	−3.403 to −0.671	0.004	−3.044	−4.987 to −1.10	0.002	−3.203	−5.131 to −1.274	0.001
HDL-C	5.163	0.940 to 9.386	0.017	11.786	4.992 to 18.580	0.001	13.484	3.678 to 23.289	0.007	10.211	0.149 to 20.274	0.047
LDL-C	–	–	–	3.220	1.472 to 4.968	<0.001	4.238	1.778 to 6.699	0.001	3.742	1.134 to 6.351	0.005
TG	–	–	–	4.039	2.039 to 6.040	<0.001	5.461	2.967 to 7.955	<0.001	5.360	2.678 to 8.041	<0.001
Smoking status	–	–	–	–	–	–	–	–	–	−6.316	−10.386 to −2.247	0.002

Subjects were divided into four groups. In each segmented multiple stepwise regression model, arousal index was the dependent variable, and age, sex, BMI, WHR, blood glucose, IR, hypertension, ESS and serum lipids profile were the independent variables. Variables were entered or removed from the model depending on the significance of the F-value.

–, means covariant was not a risk factor in corresponding models; AHI, apnoea–hypopnea index; BMI, body mass index; ESS, Epworth Sleepiness Scale score; HDL-C, high-density lipoprotein cholesterol; IR, insulin resistance index; LDL-C, low-density lipoprotein cholesterol; TG, triglyceride; WHR, waist to hip ratio; β, regression coefficient.