Sounds like a side effect of dementia to me.
Studies of the prevalence of sexually disinhibited behaviour in people with dementia report rates of 2Â17%. Burns et al (1990) found that 6.9% of 178 people with AlzheimerÂs disease living at home, in residential care or in hospital showed sexually inappropriate behaviour (exposure, obscene sex language, masturbation, propositioning others), with about equal frequency in men (8%) and women (7%). There was a significant positive association with severity of dementia.
As with much of the existing dementia treatments, there's not much they can do to treat it except give drugs which often have severe side effects.
Cheers,
Scott.