Comorbidities General group (n=32) Heavy group (n=31) χ2 P value
Hypertension 9 15 2.741 0.098
Diabetes 3 9 3.946 0.047
Coronary heart disease 0 2 NA 0.238
Tumor 1 2 0.001 0.978
Lung Disease 2 1 0 1