Popular wisdom says that a sound sleep can protect you from getting sick, and there’s a ton of scientific evidence to support this claim. There’s a physiological reason you’re inclined to sleep more when you’re sick: the health of your immune system rests (pun intended) on the duration and quality of your sleep. This is true to such an extreme degree that, according to a few landmark studies, the effectiveness of certain vaccines suffers if you don’t sleep enough after getting them.
Response to both the hepatitis A and hepatitis B vaccines seems to be negatively influenced by sleep deprivation. In one study, getting fewer than six hours of sleep made people more than ten times more likely to be unprotected after the standard hepatitis B vaccine than people who slept seven hours or more.
When you think about it, it’s quite profound that sleeping for just a couple hours more per night can affect your vaccine response so dramatically. Keep that in mind next you time you opt to stay up an extra hour or two thinking that it won’t make a big difference in your health.
What about sleep and defending yourself from the common cold? The research on this subject is fairly clear cut. People who sleep fewer than six hours are more than twice as likely to get the common cold. Similar results have been obtained for studies about sleep and the flu.
Since the immune system is extremely complex, it’s not entirely clear how sleep deprivation suppresses it, but the gist is that the number of T-cells, important cells that help your body recognize and fight infection, goes down when we’re sleep-deprived. In addition, levels of inflammation go up with sleep deprivation, which makes you more susceptible not only to the cold and flu but to serious, chronic conditions like diabetes and heart disease.
You can’t control all the variables, and getting enough sleep is no guarantee that you won’t get sick, but it remains one of the most important things you can do to make your body as resistant to infection as possible.