New research has shown that the partners of people with dementia could be as much as six times more likely to develop the condition themselves.
Experts from the University of Utah in the US said the stress and depression of watching a spouse suffer could increase the chances of dementia.
According to the survey, in which 1,221 married couples were involved, husbands are at higher risk of developing the condition.
The study was carried out on couples were dementia was present, and data was compared with couples where it was not present.
The research found that more than 200 people were diagnosed with dementia over the course of a 12-year period in the state.
A total of 125 cases of dementia only in the husband were diagnosed, 70 only in the wife, and 30 where both spouses were diagnosed (60 people).
The authors, writing in the Journal of the American Geriatrics Society, said stress may play a key role in increasing the risk of dementia although further study was needed on shared lifestyle factors and environment, which could have an effect.
They noted that people caring for a loved one with dementia report more stress and the need to provide more support than those who are caring for somebody with a physical disability.
The authors concluded: “The chronic and often severe stress associated with dementia caregiving may exert substantial risk for the development of dementia in spouse caregivers.”