The sentence is in active voice as the subject 'Ten to fifteen percent of adults' performs the action.
The sentence 'Ten to fifteen percent of adults have suffered at some point from a sleep problem called Insomnia' is in active voice.
In active voice, the subject performs the action, while in passive voice, the subject receives the action. In this sentence, the subject 'Ten to fifteen percent of adults' is the one who has suffered from insomnia, indicating active voice.
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