Segmented multivariate stepwise regression analysis (dependent variable—apnoea-hypopnea index (AHI))
| 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 |
| Age | 0.025 | 0.007 to 0.043 | 0.007 | – | – | – | – | – | – | −0.247 | −0.324 to −0.169 | <0.001 |
| Sex | −0.636 | −1.122 to −0.015 | 0.010 | – | – | – | – | – | – | 7.267 | 4.345 to 10.190 | <0.001 |
| BMI | – | – | – | 0.163 | 0.017 to 0.308 | 0.029 | – | – | – | 0.370 | 0.135 to 0.605 | 0.002 |
| WHR | 6.601 | 3.140 to 10.061 | <0.001 | – | – | – | 16.671 | 6.08 to 27.26 | 0.002 | 19.834 | 3.309 to 36.360 | 0.019 |
| Glucose | – | – | – | – | – | – | – | – | – | 1.198 | 0.412 to 1.984 | 0.003 |
| IR | 0.720 | 0.386 to 1.054 | <0.001 | – | – | – | – | – | – | 2.793 | 1.299 to 4.287 | <0.001 |
| ESS | 0.065 | 0.026 to 0.105 | 0.001 | – | – | – | – | – | – | 0.178 | 0.048 to 0.307 | 0.007 |
| Presence of hypertension | 0.695 | 0.096 to 1.295 | 0.023 | – | – | – | – | – | – | 2.325 | 0.723 to 3.927 | 0.005 |
| Smoking status | 0.571 | 0.096 to 1.047 | 0.018 | – | – | – | – | – | – | −2.830 | −4.371 to −1.288 | <0.001 |
| LDL-C | 0.331 | 0.083 to 0.579 | 0.009 | – | – | – | – | – | – | – | – | – |
Subjects were divided into four groups. In each segmented multiple stepwise regression model, AHI, 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.
–, covariant was not a risk factor in the corresponding models; AHI, apnoea–hypopnea index; BMI, body mass index; ESS, Epworth Sleepiness Scale score; IR, insulin resistance index; LDL-C, low-density lipoprotein cholesterol; WHR, waist circumference/hip circumference ratio; β, regression coefficient.