An Iowa jury on Wednesday found Henry Rayhons not guilty of charges that he sexually abused his wife, an Alzheimer’s patient, by having sex with her in a nursing home after staff members told him she was cognitively unable to give consent.

In the highly unusual case, Mr. Rayhons, 78, a farmer and former Republican state legislator who by all accounts had a mutually loving relationship with his wife, faced a felony charge that could have resulted in up to 10 years in prison.

The case ignited intense national discussion of an issue that will only gain importance as more Americans get older: whether and when people with dementia are capable of indicating if they desire intimacy.

Mr. Rayhons testified that his wife, Donna Rayhons, continued to desire and even initiate sexual contact. But he said that on the night in question, May 23, 2014, he and she had just kissed and held hands after he drew a curtain around her bed in a shared room.