Study Reveals Bacteria Are the Real Boogeyman Hiding Inside Your Bed

There are few greater fears for a New Yorker than the threat of bed bugs. The only advantage to those blood-sucking critters is that you discover them pretty quickly. In general until that day comes, there’s little cause for bed-related concerns. At least that’s what we’d all like to think. But what about all the organisms living in our beds we can’t see with the naked eye?

This was precisely what the mattress company Amerisleep recently sought to uncover through a study of bacteria present in our beds. Spoiler alert: the findings are pretty disturbing. (The rather obvious disclaimer here: yes, this was a study conducted by a company that sells mattresses and is thus probably worth reading with a grain of salt.)

For the study, Amerisleep conducted a microscopic analysis of three volunteers’ bedding that went unwashed over the course of a month. At the start of each week, the volunteers’ sheets and pillowcases were swabbed for bacterial samples. A different set of volunteers also provided samples taken from their mattresses ranging in age from one to seven years old.

Here’s where it gets gross. According to the findings, after week one the bedding contained between “three million and five million CFUs (colony-forming units) per square inch.” By the end of the study that figure had roughly tripled. To put that in perspective, according to the study in just a week an unwashed pillowcase accumulates up to 17,000 times the amount of bacteria typically found on a toilet seat. Some other fun comparisons are listed below.


OK, now we know that unwashed beds gather a lot of bacteria. So what? According to the study “gram-negative rods” were the most common of the “four main strains of bacteria” identified at over 41 percent. For the unacquainted, these are the very same bacteria that cause “pneumonia and other kinds of infections” as well as contributing to “antibiotic resistance, according to the CDC.” Bacilli was another popular bacteria identified, and when it’s not living in your bed you can find it causing food poisoning.

As far as distribution of the bacteria goes, the study found that sheets tended to carry more of the gram-negative rods, while pillowcases were more burdened with bacilli, as shown below.


The findings for the mattresses were similarly off-putting. In seven years, mattresses go from housing around three million CFUs of bacteria to over 16 million. And just like the bedding, by year seven the mattress had all four types of bacteria.

Regardless of whether you’ve been driven to purchase a new mattress, there are several important takeaways provided by this study. For one, don’t wait a month to wash your sheets. If this wasn’t self-evident before, the next time you get sick keep in mind what sort of surface you’ve been sleeping on.

Oh and of course the part you were expecting, because washing a mattress is not really an option, Amerisleep suggests replacing yours “typically every seven years.”

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