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Wendy Williams, the former daytime talk show host, has been diagnosed with frontotemporal dementia and aphasia, a disorder that makes it difficult or impossible for a person to express or comprehend language, according to a statement from her representatives.

Ms. Williams, 59, who hosted “The Wendy Williams Show” on Fox for more than a decade, was officially diagnosed last year after “undergoing a battery of medical tests,” according to a statement released on Thursday.

The tests show that Ms. Williams has primary progressive aphasia, a type of frontotemporal dementia, her representatives said, adding that she was receiving the necessary medical care.

“Over the past few years, questions have been raised at times about Wendy’s ability to process information,” the statement said, “and many have speculated about Wendy’s condition, particularly when she began to lose words, act erratically at times, and have difficulty understanding financial transactions.”

The statement was released before the premiere this Saturday of “Where Is Wendy Williams?” a Lifetime network two-part documentary about Ms. Williams.

The project stopped filming in April, when, according to the documentary, Ms. Williams entered a care center where she has been ever since, People magazine reported on Wednesday. Ms. Williams’s son, Kevin Hunter Jr., says in the documentary that doctors have connected her cognitive issues to alcohol use, People reported. Ms. Williams’s family told People that a court-appointed legal guardian was the only person who had “unfettered” access to her.