Sleep is the new sex. Or at least that's the case for millions of married couples who are challenging expectations of marital bliss by sleeping in separate bedrooms. It's not about sex -- there's still plenty of that going on.
It's more about the snoring, duvet snatching, teeth grinding and -- let's face it -- wind-breaking that has driven many a spouse to take refuge in the spare room.
"Sleep is the most selfish thing you can do. You can't share your sleep with somebody else," says Dr. Neil Stanley a sleep expert at Norfolk and Norwich University Hospital who believes that sleeping apart from your spouse promotes a happier -- and much healthier -- marriage.
"We know that people who have poor sleep have higher rates of divorce. They're more miserable. They're more depressed."
A recent survey by the U.S. National Sleep Foundation found that one-in-four married Americans is now sleeping alone.
And a new study of American builders and architects predicted that by 2015, more than 60 percent of high-end custom-built houses would have two separate master bedrooms.
"There's a definite demand for his-and-hers bedrooms," says Gopal Ahluwalia of the National Association of Home Builders, which conducted the survey. "It started with closets and bathrooms and now the trend is for bedrooms."
Even many celebrities see the benefits of sleeping solo.
The actress Helena Bonham Carter and her partner, film director Tim Burton, sleep in their own -- albeit attached -- houses.
Even Tom Cruise and Katie Holmes, who reportedly slept in separate rooms while they were dating, have kept the same arrangement since their 2006 marriage.
"Now that they are married, they don't feel the need to alter the arrangement," says a Hollywood source. "Tom has his master bedroom and Katie has hers.
"In fact, they even joke about having separate bedrooms to their friends. Katie says Tom snores and this way she can get her beauty sleep."
A partner who snores is one of the main reasons why many couples choose to sleep separately, says Stanley. But a huge cultural taboo surrounding the sanctity of the marital bed prevents them from openly discussing their new sleeping arrangements.
"A lot of people, mainly middle-aged women, relocate in the middle of the night by going to the back bedroom but they don't admit to it," he says.
"There should be no stigma about separate bedrooms, but there is that cultural stigma that people apply to it."
But the stigma is perpetuated because of the popular assumption that if a couple is not sleeping side-by-side, then they're not "sleeping together."
"It's just one of those bizarre things of the English language that we use the term "sleeping together" to mean both sleeping together and sex.
"Sex and sleep are entirely separate entities, whereas we have put them into almost the same activity where if you're not sleeping next to somebody then you're not having sex with them and that's just foolish in the extreme. It doesn't make sense."
Just ask Washington DC resident Laura (34) who last year banished her husband down the hall to the back room when his incessant snoring, bed-tossing and night-owl tendencies pushed their marriage to the brink.
Now that she can sleep an entire night without being kicked in the back by her unconscious husband, she suddenly feels a whole lot happier.
"I used to be an insomniac, but now I've gotten my regular sleep schedule back and sleep throughout the night," she says.
"I feel much more rested and my mood during the day has improved dramatically."
And not just her mood but also her marriage. Laura scoffs at the notion that having her husband down the hall has dampened their sex life.
"Having a special date or 'inviting' the other person over is much more exciting than making it happen when we're just lying next to one another," she says.
In the past, the monarchy and the very wealthy never shared beds -- they found it much too offensive. Even today, the Queen and Prince Phillip reportedly sleep in separate rooms.
Not until the Industrial Revolution, when families were forced out of the countryside and into crowded tiny two-room houses in the new industrial heartland, did the notion of bed sharing for married couples become popular.
And up until the mid 1970s, the vast majority of American married couples chose twin beds over doubles.
Now, married couples in the UK and Ireland who sleep in traditional double beds find themselves with only 27 inches of personal space to manouver during the night.
Yet many people are still reluctant to broach the subject of separate rooms with their partners for fear of hurting their feelings.
"We don't talk about sleep. We don't have it as a topic of conversation in a relationship," says Stanley.
"If most people said, 'Look, I still love you, I still desire you but at the end of the day do you mind if we had separate bedrooms,' their partners would probably say, 'Yes, that sounds like a brilliant idea.'"