Want more sex? Get better sleep. Want better sleep? Have more sex

Story highlights

  • Being too tired is the No. 1 reason women blame for loss of desire
  • After orgasm, our bodies release the "cuddle hormone" oxytocin, causing deep relaxation

Ian Kerner is a licensed couples therapist, writer and contributor on the topic of sex for CNN.

(CNN)If you think you're too tired for sex, you're not alone.

According to a large new study, women over age 50 who get fewer than seven hours of sleep are less likely to report being sexually active than their peers who sleep more, a problem that increases with age.
Sleep disorders can also interfere with sex. Research suggests that men with obstructive sleep apnea, a condition marked by snoring and breathing difficulties, have decreased levels of sexual activity, possibly because they produce lower amounts of testosterone. Sleep apnea can also increase the risk of cardiovascular problems, which may be related to sexual dysfunction.
    But the reverse appears to be true, too: Another recent study that looked at sleep and sex in college students found that for those in romantic relationships, every extra hour they slept corresponded to higher sexual desire, greater vaginal lubrication and a 14% increase in the chances of getting frisky the next day. That's probably because a good night's sleep leaves us feeling refreshed, relaxed and energetic -- all important for feeling sexy.
    "This type of research builds on previous research demonstrating that lifestyle behaviors influence people's sex