Contrary to popular belief, people who sleep six to seven hours a night live longer, and those who sleep eight hours or more die younger, according to the latest study ever conducted on the subject. The study, which tracked the sleeping habits of 1.1 million Americans for six years, undermines the advice of many sleep doctors who have long recommended that people get eight or nine hours of sleep every night. 'There's an old idea that people should sleep eight hours a night, which has no more scientific basis than the gold at the end of the rainbow,' said Daniel Kripke, a professor of psychiatry at the University of California at San Diego who led the study, published in a recent issue of the Archives of General Psychiatry. 'That's an old wives' tale. ' The study was not designed to answer why sleeping longer may be deleterious or whether people could extend their life span by sleeping less. But Kripke said it was possible that people who slept longer tended to suffer from sleep apnea, a condition where impaired breathing puts stress on the heart and brain. He also speculated that the need for sleep was akin to food, where getting less than people want may be better for them. The study quickly provoked cautions and criticism, with some sleep experts saying that the main problem in America's sleep habits was deprivation, not sleeping too much. 'None of this says sleep kills people,' said Daniel Buysse, a University of Pittsburgh psychiatrist and the immediate past president of the American Academy of Sleep Medicine. 'You should sleep as much as you need to feel awake, alert and attentive the next day,' Buysse added. 'I'm much more concerned about people short-changing themselves on sleep than people sleeping too long. ' Sleeplessness produces a variety of health consequences that were not measured in the study, critics said. 'The amount of sleep you get impacts how alert you are, your risk for accidents, how you perform. at work and school,' said James Walsh, president of the National Sleep Foundation, a non-profit that advocates for better sleep habits. 'There's much more to life than how long you live.' The study used data from an extensive survey conducted by the American Cancer Society from 1992 to 1998. Women sleeping 8, 9 and 10 hours a night had 13 percent, 23 percent and 41 percent higher risk of dying, respectively, than those who slept 7 hours, the study found. Men sleeping 8, 9 and 10 hours a night had 12 percent, 17 percent and 34 percent greater risk of dying within the study period. By contrast, sleeping five hours a night increased the risk for women by only 5 percent, and for men, by 11 percent. Among people who slept just three hours a night, women had a 33 percent increase in death, and men had a 19 percent increase, compared with those who slept seven hours. Kripke, the new study's leader, pointed out that relatively few people slept so little—1 in 1,000—where as almost half of all people slept eight hours or more. The study also found that taking a sleeping pill every day increased the risk of death by 25 percent. He recommended that people should not routinely take pills to get eight hours of sleep. While acknowledging that the sleeping pills used from 1992 to 1998 were not the same pills being used today, Kripke said, 'without data showing that contemporary pills are safe, these data provide the best information about whether sleeping pills are safe for long-term use. ' Kripke, whose study was funded by federal tax dollars, said doctors' recommendations that everyone get eight hours of sleep a night may have been partly influenced by the drug companies that make sleeping pills. He cited a report from a public relations firm representing the medicine Ambien, which gave money to the National Sleep Foundation to alert people about an insomnia 'public health crisis' as part of a marketing campaign. Bo