Table 3– Multivariate stepwise regression analysis of relationship of demographic, clinical and anthropomorphic factors, and indices of obstructive sleep apnoea syndrome severity and nocturnal hypoxaemia with glycosylated haemoglobin (Hb1Ac) levels

Variable	β (95% CI)	Standard β	p-value
Model 1^#
AHI	0.004 (0.003–0.005)	0.160	<0.001
Body mass index	0.012 (0.009–0.015)	0.127	<0.001
Age	0.004 (0.003–0.006)	0.093	<0.001
Smoking status	0.138 (0.102–0.174)	0.106	<0.001
Subjective sleep length	0.04 (0.029–0.051)	0.098	<0.001
Statin therapy	0.099 (0.057–0.141)	0.067	<0.001
Model 2^¶
ODI	0.003 (0.002–0.004)	0.101	<0.001
Body mass index	0.014 (0.011–0.017)	0.148	<0.001
Age	0.005 (0.004–0.006)	0.108	<0.001
Subjective sleep length	0.039 (0.027–0.05)	0.094	<0.001
Smoking status	0.138 (0.101–0.175)	0.106	<0.001
Sex	0.045 (0.011–0.08)	0.037	0.011
Statin therapy	0.092 (0.05–0.135)	0.062	<0.001
Model 3⁺
Mean S_pO₂	0.014 (0.009–0.019)	0.08	<0.001
Body mass index	0.016 (0.013–0.019)	0.168	<0.001
Age	0.005 (0.004–0.007)	0.106	<0.001
Subjective sleep length	0.039 (0.028–0.050)	0.096	<0.001
Smoking status	0.127 (0.09–0.163)	0.098	<0.001
Sex	0.054 (0.019–0.088)	0.044	0.002
Statin therapy	0.084 (0.042–0.127)	0.057	<0.001

AHI: apnoea–hypopnoea index; ODI: oxyhaemoglobin desaturation index; S_pO₂: arterial oxygen saturation measured by pulse oximetry. ^#: dependent variable, HbA1c; independent variables, AHI, waist circumference, body mass index, age, sex, active smoking, systolic blood pressure, subjective sleep length and statin use; model R²=0.093. ^¶: dependent variable, HbA1c; independent variables, ODI, waist circumference, body mass index, age, sex, active smoking, systolic blood pressure, subjective sleep length and statin use; model R²=0.081. ⁺: dependent variable, HbA1c; independent variables, mean S_pO₂, waist circumference, body mass index, age, sex, active smoking, systolic blood pressure, subjective sleep length and statin use; model R²=0.081.