I’m a lefty who sleeps on the left. Hubby claims he sleeps next to the door, but he’s slept on the right, no matter how the room is arranged since I joined him in bed.
I’d just like to add, I find it amazing how many people who missed
TWICE! 
Woman.
Slightly different situation, being a gimp and in a chair if it is a bad body day and crutches on a good body day I sleep on the side that has the most space and manuverability available for a chair.
Prior to that, the right side unless it was up against a wall. I always have gotten up at 2 - 3 am to pee and I don’t like to disturb hubby.
Ah, now with cats Banzai always slept in the corner nearest my face, and Jezabel used to sleep at my feet, but now that Banzai is dead she will sleep up near my face unless it is a during the day nam, in which case she absolutely has to snuggle my left side with me sleeping on my left side so I can snuggle her back.
Previously when we had 4 cats, I had a cat blanket as they demanded to sleep on different parts of me. Though I notice the dominant cat always seemed to sleep near my face. I think that is some sort of dominance thing somehow but I don’t know why this would be.
Any vets/animal techs out there with an explaination?
Now with 180-some votes we have ~ 20% more left sleepers than right sleepers in each gender.
Clearly something about left-sleepers makes them more likely to respond to polls.
It is interesting, and dare I say unanticipated by the OP, that many people choose their side for reasons other than simply leftness or rightness.
I have no signicant other, but the dog(s) sleep on the left, and the cat would sleep either on my back or chest.
When there is a human guest, I still sleep on the right.
I sleep on the right, on my right side. My wife sleeps on the left, on her left side. And it’s worked out this way for nearly 30 years. The cat sleeps in another room.
I sleep on the right 90% of the time at my house (away from the wall), on the left at my girlfriend’s house (against the wall). I suspect it has to do with both of us having phones etc. on our nightstands.
We switch it up every week or so. No “side of the bed” for us. Married 8 years.
My husband always tells me he must sleep closest to the door, so if anyone comes into the bedroom to attack, they have to get past him to get to me. Personally, I think he just likes being closer to the bathroom.
And that backfired on him when our kids were babies, and he had to be the one to get up with them in the middle of the night because he was closer to the door. 
I prefer to sleep on the top of the bed.
I sleep on my left side because that’s how I did it from age 4-18, when I slept with the bed against the right wall and I had to sleep facing left (toward the open room) because I was afraid someone (monsters when I was younger, humans when I was older) would sneak up and attack me if I slept on my right side facing the wall.
Now sleeping on my right side simply feels weird and I can’t get comfortable until I shift to my left.
Regardless of my response, there’s a person who’s also a woman sleeping on the other side. It has to do with handedness.
Heh. I sleep on the left, but it’s pretty arbitrary, since I can pick whichever corner I can squeeze into.
Early in our relationship, I told my wife she was going to have to pick a side of the bed to be hers, as I was tired of getting squeezed into the edges. She told me she was picking “the top.” :smack:
You now know virtually everything there is to know about our relationship.
I chose sleep on the right, but that’s more of a coincidence. I generally just prefer to sleep on the side next to the wall. I’d rather hit that than roll out of bed.
I answered the poll but it’s changed each time we’ve moved, switch beds, moved furniture and so forth. It’s not a hangup here.
I sleep on the right, closest to the door, and, more importantly, the bathroom. But that is not the reason, for in our last house I still slept on the right which was furthest from the bathroom. I don’t know how we picked these sides, but it has been this way ever since we got married.
The downside is that my side is closest to where the dogs sleep, so they get me up when they get hungry in the morning. Luckily I need a lot less sleep than my wife.
As for side I sleep on in the other sense, I always start on my left and wind up on my right.
Nail on the head, my friend. 
J/k ~ I just tend to involve myself with people that turn out to be mentally ill. Plus I’m kind of a bitch.
Ah yes, zombie cats do have a love of faces.
… What?
I voted that I sleep on the right side but that only holds true for our bed at home. My wife wants to be closest to the bathroom, so depending on where we sleep (staying over at a friend’s house, at a hotel, etc…) I could be on either side.
But when I sleep with two ladies, I get the middle.
When my boyfriend and I share his bed, I sleep on the left and he on the right. When we share mine, the sides are reversed. When I’m alone in either bed, I tend to sprawl diagonally across the mattress (with accomodations made for cats at my place).