Always feeling run down and catching colds? It could be because you're not getting enough shut-eye.
According to a new study published in the journal Sleep, being sleep-deprived seriously increases our chance of getting sick.
Researchers at the University of California studied the sleeping habits of 164 volunteers in the US, and compared this with their propensity to fall ill. On average, they found people who got fewer than six hours sleep a night were 4.2 times more likely to catch a cold than those who got more than seven hours.
The situation was even worse for those who routinely got less than five hours' sleep a night - they were 4.5 times more likely to catch a cold.
In fact, lack of sleep was found to be the sole significant contributor to a poor immune system. The effects of diet, smoking, stress and alcohol use, all of which were also taken into account in the study, didn't match those of sleep.
Aric Prather, lead author of the study, said the findings only added to an already huge wealth of evidence that sleep is extremely important for health:
“Short sleep was more important than any other factor in predicting subjects' likelihood of catching cold,” he said.
It didn't matter how old people were, their stress levels, their race, education or income. It didn't matter if they were a smoker. With all those things taken into account, statistically sleep still carried the day.
Previous studies into the effects of sleep have also shown it significantly affects work performance, with concentration and productivity improving after a good night's sleep. Prather commented:
In our busy culture, there's still a fair amount of pride about not having to sleep and getting a lot of work done. We need more studies like this to begin to drive home that sleep is critical to our wellbeing.
Londoners aren't doing too badly
While the busy lives of City workers don't lend themselves to long and leisurely lie-ins, compared to people in the majority of big cities Londoners manage to get a reasonable amount of rest.
Figures released last year by SleepCycle, which monitors the sleeping patterns of people in 54 major cities across the world, showed people in the capital get an average of seven hours and 26 minutes' slumber each night – more than most.
This is better than New York, where people get an average of seven hours and 10 minutes sleep each night.