There has been a lot of press about this, so I thought I would review this article published this month in the Sleep Journal. The premise of the article is that sleep deprivation has been shown to affect the immune system. But this study set out to determine if sleep duration would predict if patients would respond to Hepatitis B vaccinations.
Researchers studied 125 healthy subjects aged 40-60 years old. They had the patients record sleep diaries and rated their sleep quality for 3 days before and after each of three Hep B vaccination injections. After the study was started, they did measure 104 patients sleep with a home sleep test, called an actigraph.
The researchers broke up sleep into three categories - less than 6 hours, 6-7 hours, and more than 7 hours. The results showed that the shorter the sleep duration, the lower the response to the vaccinations. The findings were independent of age, sex, and BMI, which apparently have beeen shown to affect vaccination response. Only sleep duration, not sleep quality or sleep efficiency, was correlated with vaccination response.
The researchers did not measure daytime sleepiness. So it is not known if the subjects who got 6 hours but were not sleepy also had a decreased immune response. In other words, this study does not tell us if sleep deprivation (needing 8 hours, but only getting 6 hours) or just getting 6 hours or less is associated with the decreased immune response. Some people are short sleepers, needing only 4-6 hours of sleep per night. Do they really have lowered immune response? My intuition is that sleep deprived individuals would have the lowered immune response, not short sleepers. Perhaps experiements should be done on those who sleep 8 hours, but need to sleep 10 hours. So it may not be the absolute number of hours of sleep, just the number of hours obtained relative to the number hours needed to feel rested.