4112
A total of 11 , 373 patients were included and exposures were divided into three groups of ages <= 6 years old , 7 - 12 years and > 12 years .
 None
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 None