From the BBC
Sharing a bed with someone could temporarily reduce your brain power - at least if you are a man - Austrian scientists suggest.
When men spend the night with a bed mate their sleep is disturbed, whether they make love or not, and this impairs their mental ability the next day.
The lack of sleep also increases a man's stress hormone levels.
According to the New Scientist study, women who share a bed fare better because they sleep more deeply.