Just the smell of strong coffee is enough to wake you up, say researchers led by Yoshinori Masuo at the National Institute of Advanced Industrial Science and Technology in Tsukuba, Japan,

The research team conducted tests on sleep-starved rats and found the aroma boosted genes that produce chemicals in the brain to fight fatigue and sleep deprivation.

They also found that just the smell of coffee boosted the chemicals that control anxiety, making the rats less stressed.

The researchers took a group of 30 rats and deprived half of them of sleep for 24 hours.

Half of those kept awake were then exposed to the smell of roasted coffee beans.

The researchers then dissected the rats to examine their brains and detected lower levels of "messenger molecules" which show up genetic activity in the sleep-deprived rats.

But among those exposed to the smell of coffee, the messenger molecules appeared to have returned to near-normal levels in most cases.

According to the researchers the experiment has supplied the first ever clues to the possible reviving powers of coffee bean aroma.

Though no research has been done to find whether the results are applicable to humans, the researchers say that many of the genes singled out have human equivalents.

The researchers will now proceed to carry out further work to identify the molecule in the coffee responsible for the effect on the rats.