Some may think of it as a topic not to be discussed publicly, but it's one that affects each and every one of us: How often should you be changing and washing your bed sheets?

Research has shown the public cannot agree on the answer, and a new survey of 2,250 UK adults has found another split.

Almost half of single men said they don't wash their bed sheets for up to four months at a time, with 12% admitting they wash them when they remember - which could be even longer.

"That's really not a good plan," Dr Lindsay Browning, a chartered psychologist, neuroscientist and sleep expert tells Radio 1 Newsbeat.

Single women changed more often, 62% cleaning their bedding every two weeks, and couples claiming to do theirs every three weeks, according to data from a bedding company.

Why do we even need to change our bedsheets?

To cut to the chase, Dr Browning says we should be changing our sheets once a week, or every two weeks at the most.

Hygiene is a big factor, and one of the reasons is sweat. If you've ever tried sleeping in a heatwave, you'll know how difficult it can be.

"Sweat goes into the sheets making them not only smell disgusting but also become quite clogged up," according to Dr Browning.

She says we need to have airflow to feel cool when sleeping - as that's when we get the best shuteye.

But it's not just sweat that we need to think of, our own dead skin cells which we get rid of during sleep are also a concern.

"If you don't wash your bedsheets enough, your dead skin cells are going to build up in these sheets."

Sound horrible? It gets worse. That build-up means small creatures known as mites can feed off those cells, causing discomfort and skin rashes.

"You won't only be sleeping in the yuckiness of the sweat and dead skin cells, but the mites too."

Does the time of year matter?

Sort of.

"We can be slightly more forgiving in the winter months," says Dr Browning, but once a week "would be ideal".

If you're going more than every two weeks "you're getting into not so great territory".

Even though we sweat less in the winter, you're still getting rid of dead skin cells, she says.

"And you're still going to bed with slightly dirty hands, the same breath coming out of your mouth."

In the survey, 18% said showering at night, so the bed sheets don't get dirty, was a reason for not changing bedding more regularly.

Dr Browning says summer brings the added issue of hay fever and pollen.

"It's really important to wash your sheets regularly because you'll get those allergens in the bed, which will cause you to have that congestion."

A sanctuary

Forgetting (67%), not being bothered (35%), and not having any other clean bedding (22%) are some of the top reasons people say they don't change their bedding more, with 38% saying they didn't believe bedding needed washing "more often", according to the Pizuna Linens research.

Dr Browning says your bedroom should be a "sanctuary" for sleep, and "a wonderful, pleasant place where we feel happy".

She has clients who have insomnia and she says "if your sheets are not washed, and they look dirty, they smell, it's adding to that sensation that your bed isn't somewhere that you want to be".

"If we get into bed and feel relaxed, comfy and happy, and that new bedding smell helps us to feel calm and happy."