One 2005 American survey found that nearly one in four couples sleep in separate beds - mainly for the obvious reason that it gives them a better night's sleep. You might think that trading intimacy for 40 winks is a devil's bargain, suitable only for those whose marriages are heading for the rocks, but it's not necessarily that simple. Getting enough sleep is important for general health.
Studies at the University of Vienna in 2006 showed that sharing a bed with a partner, for men specifically, reduces brain power. Another study has shown that for women, sleeping with a partner can result in weight gain.
The main British guru of sleep studies is Dr Neil Stanley, who doesn't share a bed with his own wife. He is evangelical about the subject of separate beds. His studies suggest that on average, couples suffered more than 50 per cent more sleep disturbances if they shared a bed.
And, he says, sleep disturbance has a big effect on health, with an increase in incidences of depression, stroke, heart disease and respiratory failure. It's also disproportionately correlated with divorce.
"Poor sleep is bad for your physical, mental and emotional health. There is no good thing about poor sleep," says Stanley. Thus sleep disturbance is not only about your partner kicking, stealing the bedclothes and waking you up in the night going to the loo. Stanley points out that the British average is to have a double bed width of 1.37m, whereas a standard single bed is 79cm or 91cm. "That means you have nine inches (22cm) less sleeping space in your bed than your child has."
Stanley also points out that the habit of couples sleeping in double beds is a relatively recent cultural development. People moved into double beds at the beginning of the industrial revolution, when families moved into cities and found themselves short of living space. In ancient Rome, the marital bed was a place for sex, but not for sleeping.
The idea that people should sleep together out of a desire for intimacy holds little appeal for Stanley: "Sleep is the most selfish thing you can do. People say they like the feeling of having their partner next to them when they are asleep. But you have to be awake to feel that. We all know what it's like to sleep in a bed with someone and have a cuddle. But at one point you say, 'I'm going to sleep now.' At that point, why not just take yourself down the landing?"
Why not indeed? However, for me, such a move would be a radical and somewhat disturbing experiment. Sleeping alone is for old couples and couples who have no physical interest in each other any more. The marital bed isn't just a sleeping arrangement. It represents closeness, sharing, the married state. Without a bed to climb into together at the end of the day, are you really any more than two people under the same roof?
It is not always a pleasant experience to share a bed with someone. But it is rather unique and it sets the mark on the particular status of the married condition. And most couples continue to take this view - according to one survey, only 8 per cent of couples in their 40s and 50s sleep in separate rooms. The temptation does grow as you get older, though - more than 40 per cent of over 70s sleep apart.
One family therapist put it this way: "The biggest problem in every couple is disconnection. And this decreases intimacy. It starts with, 'I'm going to take this kid here and you can take the other one there'."
And sleeping alone means physical distance, which can lead to emotional distance. "A logical decision in one area has consequences in other areas."
As it happened, I spent the night before writing this column in the spare bed and I must say I had a wonderful night's sleep. I could grunt and snort to my heart's delight, shuffle about under the covers and wander off to the loo when I felt like it, without having to worry about someone silently cursing me.
I'm thinking a compromise may be in order - perhaps weekends together and weekdays apart. But another part of me thinks it's the thin end of the wedge. And the thick end of a wedge is designed to put a lot of space between objects. Already separated by technology, we will be just two people living under the same roof. That may be a relationship of sorts. But it's not a marriage.
Heavy sleepers
• A survey of 70,000 women aged over 16, published in 2005, showed that women who slept five or fewer hours a night were a third more likely to put on at least 15kg than sound sleepers. That's a big difference. So it appears that sleeping together - as it tends to result in disturbed sleep - makes you fat.
• The scientific explanation for this is that after just a few days of sleep restriction, the hormones that control appetite cause people to be hungrier. So women who sleep less might eat more.
• The result of this weight effect on men is not known.Sleeping in the same bed has been found to have negative effects on health and, for men, brain power.
- Observer
