They say that couples shouldn’t go to bed angry. I say they shouldn’t wake up angry either.

This can happen when one partner keeps the other from a good night’s rest with snoring, constant tossing and turning, trips to the bathroom, or late-night TV and reading. The result is a sleep-deprived partner who wakes up tired, cranky and resentful.

The answer for some couples is obvious but seldom discussed: separate beds in separate parts of the house.

We got in the habit years ago when my husband worked the graveyard shift. He came home at 2 or 3 in the morning, so to avoid disturbing me, he slept on the couch. We switched rooms in the morning when I woke up to get the kids ready for school. Later, he occupied our daughter’s room while she was away at college and just shut the door, snoozing through the morning ruckus.

We didn’t discuss this arrangement; it just sort of evolved as we adapted to our circumstances and our bodies demanded more quality shut-eye. Work schedules aside, this made sense on a bunch of levels:

He runs hot and I run cold, leading to passive-aggressive wrangling over covers and ceiling fan output.

We both prefer the left side of the bed.

One of us snores. And occasionally throws elbows.

That doesn’t mean we don’t cuddle before heading to our respective sleep zones.

There are physiological reasons it gets harder to share a bed as you age. According to the National Sleep Foundation, after 50, your brain waves change and you don’t reach the same level of deep, restorative slumber. Lighter sleep means it’s easier to become awakened by the stirrings of the other person in the room.

Other factors cited by the NSF for nighttime disruptions: menopausal hot flashes; restless leg syndrome, the risk for which increases after age 50; and snoring from packing on extra pounds over the years.

(If you sleep next to a snoring partner, you’re losing about an hour of sleep a night, the experts say.)

For these and other reasons, separate sleeping quarters for couples are gaining favor. In fact, more and more luxury homes are being built with two master suites, like in the days of the aristocracy.

(This reminds me of a memorable scene from “Downton Abbey” in which the snobbish Mary Crawley mocks her parents’ insistence on sharing a marital bed: “I hope you know that really smart people sleep in separate rooms.”)

When you’re young and in love, you’re perfectly content with a full-size bed scarcely wider than a twin. It’s all very cozy and cute.

But fast-forward 20 years and you’re shopping for the biggest mattress you can find that will put enough distance between the two of you so you won’t even notice you’re sharing your bed with another body. And if you can get separate mattresses all the better, even if it creates a distinct dividing line between his and hers.

So maybe you’re already sleeping in separate beds, just not in separate rooms. Yet.

No judgment here. It’s all very civilized.

Lady Mary would approve.

“She Speaks” is a weekly column by the women writers of the Honolulu Star-Advertiser. Reach Christie Wilson at cwilson@staradvertiser.com.