Although eight hours is the number most often associated with a full night's sleep, sleep experts know that there is some degree of variation when it comes to individual sleep needs. Most often, the recommendation for sleep times comes in a range of seven to nine hours, depending on the individual. The National Sleep Foundation currently recommends this seven- to nine-hour range as ideal for healthy adults.
But there is a growing body of research that suggests the ideal amount of sleep may in fact be at the very low end of that range. A number of studies indicate that seven hours -- not eight -- may be the most healthful amount of nightly sleep.