Simplify the following text for a Grade 5 native English-speaking person.
Original: The medical community began paying more attention than previously to primary sleep disorders , such as sleep apnea , as well as the role and quality of sleep in other conditions . By the 1970s in the USA , clinics and laboratories devoted to the study of sleep and sleep disorders had been founded , and a need for standards arose .
Simplified: There are many sleep disorders , and some of them are very serious .