'Knacker factors' prove key to office sleepiness

Scientists have devised a formula that can tell the 12 million Britons who struggle to stay awake at work when to expect a daytime "dip" - and also when they are most likely to feel alert.

Scientists have devised a formula that can tell the 12 million Britons who struggle to stay awake at work when to expect a daytime "dip" - and also when they are most likely to feel alert.

The formula, produced by the fatigue-management consultancy Awake, is based on circadian rhythms - the 24-hour biological clocks that determine our sleeping and waking cycles.

Awake arrived at the equation CDA + CT + KF = TMT, where CDA stands for "circadian dip in alertness", CT for "chronotype timing" - the timing of an individual's body clock - and KF for "knacker factors" such as prior sleep quality and quantity, and alcohol consumption. TMT is the time a person is likely to feel "most tired".

Dr Paul Jackson, managing director of Awake, linked to the Sleep Research Centre at Loughborough University, said: "This simple equation enables anyone to calculate what time of the day they are likely to feel most tired and schedule their activities accordingly."