According to a recent study by the National Sleep Foundation, about one in every four married or cohabitating Americans claim they're so sleep-deprived that they're often too tired to have sex.
It's not surprising why sleep trumps sex: Between work, family and social obligations, our need for shuteye often suffers.
Add in problems such as financial stress, health issues and relationship woes, and you can see why sex tends to drop to the bottom of our "to do" list -- if it's on there at all.
And when we do finally hit the sheets, many of us are more apt to hold onto our smart phone, tablet or other gadget than our partner's hand.
"Many of us are multitasking throughout the day for extended periods of time -- constant stimulation that can allow for enriching experiences," says Amy Levine, sex coach and founder of Ignite Your Pleasure. "However, that can also take its toll on our sex lives."
In some cases, though, simple exhaustion isn't the only reason why sex takes a backseat to sleep.
Unless you've been diagnosed with a health condition that saps energy, such as chronic fatigue syndrome, it's possible that factors other than a busy lifestyle are at play.
"Boredom could be to blame," Levine says. "If you think or feel sex is going to be status quo, it will feel like a chore rather than something that's satisfying."
Also likely: a low sex drive. According to a 2008 study published in the Archives of Internal Medicine, between one-third and one-half of all women will find themselves coping with low sexual desire at some point in their lives. And while we're lacking such strong statistics for men, I and many other experts believe that low libido is increasingly becoming a problem for guys, too.
Although any number of factors could be to blame for these dips in desire, many of the same triggers that make us exhausted -- like stress, anxiety, worry -- are also linked to decreased desire in both men and women. Some people may confuse a low libido with being too tired for sex; for others, exhaustion itself seems to trigger a lower sex drive.
"A lot of women are satisfied with their relationships and enjoy sex once it's under way but are just too tired and stressed to feel sexual desire," explains Laurie Mintz, a University of Florida professor of psychology and the author of "A Tired Woman's Guide to Passionate Sex."
The book was shown in a published study of 45 women to significantly increase sexual desire, arousal, satisfaction and overall sexual functioning in those who followed the book's program.
Fortunately, there's much you can do to create both the time and energy to make sex a regular part of your routine again. Try these steps to get back on track:
Get on a regular sleep schedule
It's the end of a long day, the kids are finally in bed, and all you and your partner want to do is -- well, veg out in front of the TV, or putter around on the Internet, or play a few rounds of Words with Friends.
Says Patty Brisben, educator and founder of PureRomance.com, "The average American spends 2.7 hours a day watching TV, according to the American Time Use Survey. So you have to ask yourself which is more important to you: your relationship or American Idol?"
Try to stick to a regular bedtime, and devote the last hour or so of your waking time to your partner. Even if you do nothing more than cuddle, you're setting a schedule that allows time for more when you're ready. Eventually, your mood will follow.
Think outside the box
It's easy to say, "Let's have sex tonight," early in the day when your energy is still high. Yet most of us wait until nighttime to get intimate, and by then we're often too tired to make a move.
"Some people are more aroused during the day than at night," Levine says. "Make your arousal pattern work with your schedule and that of your partner so you can enjoy physical intimacy." That might mean indulging in morning sex before work or a lunchtime quickie -- whatever works for you.
Make a date
Think scheduled sex is boring? Not necessarily. There's a common assumption that spontaneous sex is best, but "planned encounters help build anticipation and relieve tension within your relationship," Mintz says.
Get a sitter and head out for date night, play hooky from work, or make time for sex when the kids are at a friend's house, for example.
Adds Brisben, "Scheduling sex is great for someone who loves to make a 'to-do' list. You know you're not going to sleep until that box is checked off. Plus, it'll establish a pattern of healthy sexual behavior. They say it takes 21 days to form a habit. Once that habit is formed, you won't want to go to sleep unless you've had sex."
Just do it
It can be tough to feel aroused when all you want to do it sleep. But stick with it.
Like other forms of exercise, "sex can give you an energetic buzz," Levine says. "You just have to be willing to push past the feeling of tiredness to experience the pleasure that will ultimately recharge you.
"If you shift your schedule so you get enough sleep and reprioritize your day to the essentials," Levine says, "being tired doesn't have to be a factor that influences your sex life."
And remember, sex begets sex. Once you get back into the swing of things, you're likely to start wanting to get -- and stay -- intimate more often. When you wake up and smell the coffee, it will smell all the better for having had sex the night before.