A rare condition causes a lucky few to only need 6 hours of sleep a night, reports Business Insider Australia.

Sleep experts may refer to a person with short sleep syndrome as a “habitual short sleeper” (HSS) and “natural short sleeper (NSS),” says Paula G. Williams, PhD, associate professor in the department of psychology at University of Utah who has studied short sleepers.

Although approximately 30% of Americans report regular bouts of short sleep, many are not short sleepers from a clinical standpoint since they do not feel well-rested the next day.

The primary symptom of short sleep syndrome is consistently sleeping six hours or less and feeling fully functional the next day. However, from her research Williams has found other traits that tend to be consistent among most short sleepers.