SAN FRANCISCO, Aug. 2 (UPI) -- People who slept fewer than 6 hours per night were less likely to mount antibody responses to a vaccine that may leave them unprotected, U.S. researchers say.
Lead author Aric Prather -- a clinical health psychologist and Robert Wood Johnson Foundation Health & Society Scholar at University of California, San Francisco and University of California, Berkeley -- said antibodies are manufactured by the immune system to identify and neutralize foreign objects such as viruses.
The study, conducted at the University of Pittsburgh when Prather was a doctoral student, involved 70 women and 55 men ages 40 to 60. All were non-smokers in relatively good health, and all lived in Pennsylvania.
Each participant was administered the standard three-dose hepatitis B vaccine. The first and second dose were administered a month apart, followed by a booster dose at six months. Antibody levels were measured prior to the second and third vaccine injection and six months after the final vaccination.
All participants completed sleep diaries detailing their bedtime, wake time and sleep quality -- 88 subjects also wore electronic sleep monitors.
The study, published in the journal Sleep, found people who slept fewer than 6 hours on average per night were far less likely to mount antibody responses to the vaccine and were far more likely to be unprotected by the vaccine than people who slept more than 7 hours on average. Of the 125 participants, 18 did not receive adequate protection from the vaccine, the study said.
"Sleeping fewer than 6 hours conferred a significant risk of being unprotected as compared with sleeping more than 7 hours per night," the scientists wrote.