7 vs. 8: how long should we sleep?

We’ve often been told that we should aim to get eight hours of sleep every night, but new research suggests that seven hours—not eight—may be the optimal amount of sleep. According to an article in the Wall Street Journal by Sumathi Reddy, several sleep experts have recently found that seven hours of sleep produces better results on some cognitive and health measures than eight. “The lowest mortality and morbidity is with seven hours,” Shawn Youngstedt, a professor in the College of Nursing and Health Innovation at Arizona State University Phoenix, said. “Eight hours or more has consistently been shown to be hazardous.” Last year, a study in the journal “Frontiers in Human Neuroscience” gathered data from users of the cognitive-training website Lumosity. Using the self-reported sleeping habits of about 160,000 users who took spatial-memory and matching tests and about 127,000 users who took an arithmetic test, researchers found that cognitive performance increased as people got more sleep, reaching a peak at seven hours before beginning to decline. After seven hours, “increasing sleep was not any more beneficial,” Murali Doraiswamy, a professor of psychiatry at Duke University Medical Center in Durham, N.C., who co-authored the study with scientists from Lumos Labs Inc., which owns Lumosity, said. According to Doraiswamy, the study replicated earlier research, including a study on memory loss. Still, most sleep experts recommend a range of seven to nine hours of sleep a night. “I don’t think you can overdose on healthy sleep,” Safwan Badr, chief of the division of pulmonary, critical care and sleep medicine at Wayne State University School of Medicine in Detroit, said. “When you get enough sleep your body will wake you up.” Read the full article at wsj.com.]]>