While all the apps vary, they generally work by having users pick a window of time in the morning — typically 20 to 40 minutes long — during which they would like to get up, then nudging the sleeper awake at the lightest point of sleep in that window. Sleepers get a score each morning that factors in the number of hours they slept while adding and subtracting points for things like disruptions and the percentage of time spent in the deep, restorative stages of sleep. The programs also let users keep track of daily habits like caffeine intake, exercise and meals, among other things, so they can see which habits might be affecting their sleep.
But while some people swear by these tools, scientists caution that the claims they make and the advice they dole out to users may not be very sound.
“I think these are clever devices, but there’s very limited data on how valuable they are,” said Dr. David M. Rapoport, the director of the sleep medicine program at New York University School of Medicine. “They’re a really good way to capture data. But some of them are giving out recommendations in ways that just aren’t proven.”
He points out that certain features, like quantifying sleep and tracking habits, are particularly beneficial because they identify sleep patterns. “Many people lie to themselves about how much sleep they’re really getting,” he said. “If it takes an app to tell you you’re only getting four hours a night and that that’s why you’re tired, then that’s a good thing.”
But, he says, when an app instructs you to get eight hours of sleep instead of seven, or to avoid coffee after 6 p.m. for better sleep, it has gone too far, since not everyone needs the same amount of sleep or is affected in the same way by caffeine. “These apps tend to suggest that there’s a right way you should do things,” he said, “but we cannot make the same recommendations for everybody.”
By ANAHAD O’CONNOR at the New York Times