On a recent evening, Brian Pardy plunged his right hand into ice water and held it there for two and a half minutes.
Pardy was carrying out an at-home experiment that the genetic testing company 23andMe is asking its customers to perform. An early adopter of genetic testing, Pardy first bought a 23andMe test in 2012.
“It was uncomfortable and slightly painful, but nothing like wearing wet gloves and shoveling snow for an hour at 10 below zero,” says Pardy, who lives in northwest Vermont. Most people can stand to keep their hands in near-freezing water for at least 100 seconds, according to 23andMe.
The experiment Pardy did is known as a cold pressor test, and it’s one of many used to gauge a person’s tolerance to pain. It’s part of a new study 23andMe announced earlier this month to study the genetic links of pain tolerance, and it represents the company’s first foray into at-home research.
23andMe has previously launched studies on medical conditions like depression, fertility problems, and irritable bowel disease, using surveys to ask participants about things like their health history, lifestyle, and diet (see “23andMe Pulls Off Massive Crowdsourced Depression Study”). The new study also includes two surveys about pain tolerance and pain history, but this is the first time the company has asked people to do an experiment on their own and report the results.
Carrie Northover, director of research services for 23andMe, says the goal of the study is to “understand genetic factors associated with experiencing pain and response to medications that help alleviate pain.” Previous research has suggested that multiple genetic factors are at play in chronic pain, and that certain groups of people report pain more often than others.
23andMe has around two million customers who have paid $99 to $199 to have a subset of their genes profiled when they provide a vial of their saliva. About 85 percent of those people have consented to have their data used for research, according to the company, allowing 23andMe to conduct large studies on the genetic underpinnings of certain traits and diseases (see “23andMe Sells Data for Drug Search”). A separate consent form is required from people who participate in the pain study, which Pardy says he wanted to do because he suffers from back pain. He says he’d love a cure, rather than just medication to manage it.
Northover says they plan to enroll 20,000 Americans to take the two pain surveys and hope to get 10,000 of those to complete the cold pressor test over the next year. She didn’t give much detail on what 23andMe will do with the data, other than to say the results “may help develop a more personalized approach to pain medication.” 23andMe has partnered with German pharmaceutical company Grünenthal for the study.
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Ajay Wasan, vice chair for pain medicine at the University of Pittsburgh Medical Center, says the cold pressor test is only one way to measure pain. There are a range of other tests, including ones that measure a person’s tolerance to heat, pin pricks, and pressure.
“The problem is no one single experimental pain test maps really well to overall pain sensitivity and doesn’t have high correlation to someone’s clinical chronic pain or their response to treatment,” he says.
Wasan says researchers would have to look at “a whole group of stimuli” to understand a person’s pain threshold. He says his own pain tolerance varies depending on the test. For example, he can only do the cold pressor test for about 30 seconds, but his tolerance to other kinds of pain, like heat and pressure, is much higher.
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These kinds of tests are also usually administered in doctor’s offices. Wasan says he isn’t aware of any published studies in which lots of people have done a cold pressor test at home. Having people self-report their results raises questions about whether the data can be trusted.
But John Wilbanks, chief common officers at the open-science nonprofit Sage Bionetworks, says that depending on how the study is designed, patient-reported outcomes can be reliable. Wilbanks helped conceive some of the first studies for Apple’s ResearchKit, a medical software platform launched in 2015 that lets researchers collect health data about people remotely.
A study published in March in Nature Biotechnology found that the Apple platform and a smartphone app were fairly accurate in gathering data about asthma patients, relative to existing patient studies.
In the 23andMe study, users log in to an online interface that times them while they take the cold pressor test. The “timer” is designed to simply pulse instead of flashing a time, which is meant to discourage people from trying to “beat the clock,” Northover says. Still, that won’t necessarily stop participants from reporting false data.
23andMe won’t be able to tell whether that’s happening until some people have already taken the test. The company will analyze data from the test partway through the study to make sure the results are valid. “We should see similar distributions in responses compared to what’s in the published literature,” Northover says.
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