Dr Murray said the loss of an hour’s sleep could exacerbate the effects of sleep deprivation and has been shown in studies to contribute to an increase in road accidents in the week after the introduction of daylight saving. ‘‘A study published in the New England Journal of Medicine in 2008 also revealed an increase of between 5 per cent and 10 per cent in heart attacks in the week after, with the peak coming on the Tuesday,’’ he said. ‘‘And the rates of heart attacks fell when daylight saving ended and people received an extra hour of sleep.’’

He said the problems were greatest for those who already suffered from sleep deprivation. ‘‘It has also been associated with road rage,’’ he said. Other acute affects include a decrease in alertness, concentration and mental performance. People sleep best when their body clock is in synch with their level of tiredness. Dr Murray compares the loss of an hour’s sleep and the sudden change to the hours of daylight to jet lag. ‘‘You can travel for 20 hours on a plane and be exhausted but not be able to sleep because your body is telling you it is the wrong time.’’ Those most prone to difficulties are night owls and adolescents who frequently stay up late. Dr Murray said going to bed earlier is unlikely to work. ‘‘The trick is to get up earlier and get more exposure to sunlight in the morning.’’

In most cases, people make the adjustments to their body clock within two weeks. But Dr Murray said some people never adjusted to the change. Queensland, Western Australia and the Northern Territory do not have daylight saving. In March, Western Australia ended a three-year daylight saving trial ahead of a defeated referendum. Daylight saving will end on Sunday, April 4, 2010.