i4 + (x X t3) + (y X i1) - a1 - t4 + t2 - i3 + (2 X (p+p2)) + L1 = cold cure

If there's anything worse than having a cold, it's being kept up all night by a cold. But salvation is at hand. All you have to do is: i4 + (x X t3) + (y X i1) - a1 - t4 + t2 – i3 + (2 X (p+p2)) + L1.

This, er, simple formula is the brainchild of Dr Chris Idzikowski, the director of the Edinburgh Sleep Centre. It is based on a survey of 2,000 people and combines four groups of factors that influence getting to sleep when you're sick: temperature, position, light and the food and drink you've taken.

Taking a hot bath (t2 in the formula) before bed opens capillaries in the skin, so that the body can shed heat after you get out of the tub. And opening a window (y) for fresh air makes breathing easier. Watching the telly (a1) is a distraction to be avoided.

Late-night channel surfing is just one of the things people should avoid when they prepare for bed with a stuffy nose and a throbbing head, said Dr Idzikowski. Bed socks (t4) and hot water bottles actually make it harder to sleep, he added. "The brain wants to lower the body temperature for sleep. You don't want to catch a chill but you shouldn't be too warm."

Another mistake sick people make is to take a sedative, which depresses breathing. Patent medicines (i4), particularly those containing paracetemol, can reduce symptoms such as headaches, but decongestants make it harder for the body to fight the virus.

More controversial is the role of alcohol. Dr Idzikowski suggested a hot toddy (i1) before bed will help to relax the sufferer, but not more than two units (x).

The final surprise is that the bug itself helps to make people sleep. Virus fragments are similar to sleep-inducing chemicals in the brain, said Dr Idzikowski.

Further reading: 'The Insomnia Kit: Everything You Need for a Good Night's Sleep', by Dr Chris Idzikowski (Newleaf)