When the weather outside is reaching Baltic levels (for the UK, anyway), it's tempting to leave the heating on all night so that you wake up nice and toasty.
However, this could be doing more damage than good - and we're not just talking about your electricity bills. In fact, it could be the reason you can't shift that grizzly cold.
Research has shown that almost half of people who sleep with their heating on overnight report feeling ill the next day.
The survey, conducted by Slumberdown, found that 46 percent of people who slept with their heating on felt sick in the morning, with 37 percent reporting symptoms including headaches, dry mouth and dehydration.
Meanwhile, one in five people reported waking up in the night with a sweat on, which is never a good thing to wake up to.
Slumberdown sleep expert Professor Jason Ellis said: "Our bodies do a great deal of work for us during sleep.
"As part of that process, our body temperature changes over the course of the night and we tend to cool down towards bedtime and then naturally warm up towards the morning.
"As such, we may go to bed warm and cosy but as the research shows, wake up hot and bothered. The key is being comfortable when going to bed and staying comfortable throughout the night.
"The more comfortable you are the less likely you will wake during the night or too early in the morning."
What's more, the minute you step outside for that dreaded commute, your body is being launched from one extreme to the other.
Dr Maurice Pye, consultant cardiologist at York Hospital, told The Daily Mail: "Temperature changes can affect the circulation quite dramatically.
"If you go from hot to cold, that can increase your blood pressure in a way that can affect blood supply to the heart. It causes a reflex that narrows the arteries, which reduces the blood supply to the heart muscle. This can cause angina, heart attacks or changes in heart rhythm.
"We have angina patients who say they're fine in most rooms, but as soon as they go upstairs to the bedroom, where it's perhaps cooler, they get chest pain."
But that doesn't mean you need to wake up to a frosty room, nor does it mean your heart is going to shut down if you keep your heating on at home.
As is often the case in life, moderation is key. Dr Pye says to aim for a 'reasonable temperature' during the night, above 18c, throughout all the rooms you use regularly.
And perhaps invest in some toasty PJ's while you're at it, just for safe measure.