表 1. Results of stepwise regression for feature selection.

逐步回归特征选择结果

Feature	Deviation	χ2	P
Preoperative sleep disturbance after admission	3241.461	500.657	<0.001
Type of ward (rooms for 4 or more patients)	3201.410	40.051	<0.001
Body mass index (underweight)	3191.251	10.159	0.001
Smoking	3183.092	8.160	0.004
Range of diseases (bilateral)	3176.368	6.724	0.001
Joint mobility (flexion)	3169.883	6.486	0.012
Joint mobility (extension)	3147.234	6.123	0.013
Hemoglobin (anemia)	3135.324	5.554	0.018
Surgery type (knee arthroplasty)	3120.740	4.405	0.036