Table 2.

Spearman’s correlation coefficients between physiological variables and the apnea–hypopnea index, both overall and for patients with obstructive sleep apnea only

Variable	Apnea–Hypopnea Index Overall (n = 51)	Apnea–Hypopnea Index OSA Group (n = 29)
Age, yr	−0.28*	0.12
BMI,† kg/m2	0.48‡	0.29
Pack-years§	−0.03	0.21
CT-derived percent emphysema†	−0.41‡	−0.42*
CT-derived percent gas trapping†	−0.44‡	−0.49*
TST, min	−0.21	−0.40*
Sleep efficiency, %	−0.31*	−0.37*
Arousal index, events/h	0.47‡	0.47‡
Mean SaO2, %	−0.16	0.03
Lowest SaO2, %	−0.29*	−0.01
Percent TST SaO2 <90%	0.22	0.16
Sleep architecture, % TST
Stage N1	0.16	0.47‡
Stage N2	−0.02	−0.02
Stage N3	0.11	−0.14
Stage REM	−0.18	−0.21

Definition of abbreviations: BMI = body mass index; CT=computed tomography; OSA = obstructive sleep apnea; REM = rapid eye movement; TST = total sleep time.

^*P < 0.05.

^†Missing values for BMI, CT-derived percent emphysema, and CT-derived percent gas trapping for the OSA/no OSA groups: 1/1, 9/5, and 15/10, respectively.

^‡P < 0.01.

^§According to American Thoracic Society guidelines.