2157
Follow - up air conduction done at least 6 months after end of treatment showed an adjusted mean difference in hearing thresholds of 1 . 08 dB ( - 0 . 81 to 2 . 96 dB ; P = 0 . 26 ) between treatment arms .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Disease, Chemical 
Text: {0} 
Answer:
 None