Getting less sleep than a person should can result in a weakened immune system, increasing the chances that one can get sick. Some experts point out that if a person gets only five hours of sleep per night over a period of five days, his or her immune system is weakened by 50%. One study showed that participants who slept fewer than seven hours a night and were then exposed to a cold virus were three times as likely to come down with a cold as study participants who got at least eight hours of sleep per night.
More about sleep and illnesses:
Doctors recommend that the average adult get seven to eight hours of sleep every night. Children and teenagers should get at least nine hours.
During sleep, people produce substances called cytokines that are crucial in fighting off infection. Less sleep means fewer cytokines, increasing a person’s susceptibility to illness.
Adults who oversleep are generally at a greater risk of developing health problems such as obesity, depression and heart trouble. Oversleeping in adults is defined as more than nine or 10 hours per night.