We can know from this article that insomnia is a disease which prevents people from a sound sleep and a majority of American adults suffer from insomnia,finding it difficult to sleep well. (finding it difficult to sleep well 为分词做状语)
Through this article, we learned that insomnia can not sleep a full night's disease and insomnia among adults in the United States accounted for the majority, they generally find it difficult to believe that during sleep.