In 2000, a Wall Street Journal writer granted a huge boon to the mattress industry, by publishing the claim that a mattress doubled in weight after 10 years, due to the effects of sweat, dead skin, hair and dust mites that feed on that dead skin.
How accurate is that? Not very but it will gain weight. Obviously most people use sheets and pillow cases, which get washed, but most people are also cheap and keep their homes abut 78 degrees in the summer. Mites love a moist, warm environment and sweat makes a difference in that even if you wash your sheets often. A used mattress may have 10 million of them living there - that weight begins to add up over time.
If your mattress has actually doubled in weight, you probably have a much bigger problem than an allergy to dust mite feces (though filter and vacuum manufacturers like the concept of a dirty mattress as much as mattress salespeople do) - and if dead skin is not enough to get you running to the store, a new study found a variety of bacteria, yeasts and molds. Tests by Microtech Services Ltd in the UK found Enterobacteriaceae, E. coli and Staphylococcus aureus bacteria, along with Cladosporium on the top layer plus Aspergillus and Saprophytic molds deeper within the mattress.
Ew! But rest assured, you can minimize the gross. Watch the video to see how. And if you are too cheap to get a new mattress, you can always invoke the hygiene hypothesis and claim it makes you healthier.