Sharing your bed can reduce your brain power - but only if you are a
man, say scientists.
When men spend the night in the same bed as someone else their sleep patterns
are disturbed, even if they do not make love, new research shows.
And this leads to poorer performance in mental agility tests the next day.
However women do not suffer the same problem. They too have disturbed sleep
if they share a bed, but tend to get better quality rest when they do finally
drop off. This means their brain power remains undiminished.
The finding suggests that if a man has an important day ahead he would be
best to head off to the spare room to sleep rather than sharing the marital bed.
The new research, featured in New Scientist magazine (must keep) was
presented to the Forum of European Neurosciences in Vienna, Austria, last week.
A team led by Professor Gerhard Kloesch at the University of Vienna recruited
eight unmarried, childless couples in their twenties for their study.
He asked them to spend 10 nights sleeping apart and ten together while he
monitored their rest patterns at night through wrist monitors and sleep diaries.
The next day he gave them mental ability or 'cognitive' tests.
Even without having sex, everyone had more disturbed sleep when sharing a bed
than alone but the effects of this on the brain only affected the men.
According to the journal: "Lack of sleep led to increased stress hormone
levels in men and reduced their ability to perform simple cognitive tests the
next day."
However women seemed to show no such ill-effects even if their sleep was just
as disturbed. The researchers found women were more refreshed than men even when
they slept the same number of hours and so concluded they must sleep more
deeply.
The study also found sharing a bed can impact on dreams. Typically women
remembered more of their dreams after sleeping alone while men recalled the most
after sex.
Interestingly, most men were not aware that sharing their bed disrupted their
sleep - and in fact believe having a partner there helped them drop off.
Women typically felt they slept better when alone, although this makes no
difference to their mental performance the next day.
Professor Jim Horne, who runs the Sleep Research Centre at Loughborough
University said: "Men would need a really bad night's sleep for their brain's
performance to be impaired the next day.
"Also, couples who share a bed for years get used to each other so much that
if they then spend a night apart they actually have a worse night's sleep alone
than when together."
