From when women get tired at night to men having more trouble falling asleep, a Cosmopolitan report details several difference in how men and women sleep.

Anyone who’s ever shared a bed with a guy can tell you that men and women don’t always see shut-eye to shut-eye when it comes to sleep — regardless of your daytime (or sexual) chemistry. Here’s why:

1. Women get tired earlier in the evening. Your circadian rhythm is one system that moderates your body’s natural sense of when it’s supposed to sleep and wake up. Among women, this system starts to spew out signals for bedtime about two hours earlier than it does for men, according to Diane Boivin, MD, director of the Centre for Study and Treatment of Circadian Rhythms at McGill University’s Douglas Mental Health University Institute, where she recently coauthored a study on the topic.

2. Men have more trouble falling asleep early. It’s no wonder he tosses and turns when you both hit the sack at your bedtime: Men’s sleep cues kick in roughly two hours later than women’s. And when your natural clocks effectively operate as if you’re stationed in two different time zones, you’re unlikely to fall asleep at the exact same time — particularly when he goes to sleep at your bedtime.

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