who dog sleeps with

The answer is, "the dog."

who dog sleeps with

I know that's not a scientific finding, but it's still true. Dogs are the most popular bed companions in America. About half of all Americans have a dog, and one-third of those who don't own a dog say they would like to. A survey by the American Pet Products Association found that among owners with dogs, 54 percent sleep with their pet at least some of the time.
That makes sense because dogs are good for our health and happiness in so many ways — from lowering stress levels to preventing heart disease. A study published last year found that people who live with dogs have lower blood pressure than those who don't. And having a pet can reduce the risk of heart attacks by more than 50 percent and lower the risk of stroke by almost 40 percent, according to research conducted at Harvard Medical School and reported in 2010 by The New York Times.
That's why researchers are starting to look at how pets affect our sleep patterns. A study published last month found that having a dog in bed improves sleep quality by reducing stress hormones like cortisol as well as boosting serotonin levels — which leads to better moods during the day.