TIME HIV/AIDS

This Contraceptive Is Linked to a Higher Risk of HIV

Depending on the contraceptive they’re using, women may be at higher risk of getting HIV

When it comes to the double duty of preventing both pregnancy and HIV, condoms are the best option, especially in the developing world where treatment for the infectious disease is harder to access. But the same isn’t true of other contraceptive methods, according to the latest study in Lancet Infectious Diseases.

Lauren Ralph, an epidemiologist at University of California San Francisco, and her colleagues conducted a review of all of the available studies on hormonal contraceptive methods—including injections of Depo Provera and Net-En that work to prevent pregnancy for about 12 weeks, as well as the pill. Among 12 studies involving nearly 40,000 women in sub-Saharan Africa, those using Depo showed a 40% higher risk of getting HIV than those using other methods or no contraception at all.

Previous studies suggested that Depo, which is made up of a hormone that mimics the reproductive hormone progesterone, was linked to higher risk of infection, but other studies showed conflicting results. Ralph found that only Depo was associated with a higher risk of HIV infection; there was no similar increase among women using the pill, which is composed of two hormones, estrogen and a form of progesterone. The correlation remained even after they considered potentially confounding factors, such as the women’s condom use.

While the study didn’t address the reason for the difference between oral contraception and Depo, some research suggests that their differing hormone combinations may have varying effects on the structure of the genital tract, a woman’s immune response or her vaginal flora, all of which could influence her vulnerability to acquiring HIV.

The results raise a difficult question about whether the increased risk of HIV infection warrants removing Depo from a woman’s contraceptive options in places like Africa. Worldwide, according to the authors, 41 million women use injectable contraception, and they have played a role in lowering death and health complications among women of child-bearing age. “Whether the risk of HIV observed in our study merits complete withdrawal of hormonal contraception, especially Depo, needs to be balanced against the known benefits of highly effective contraception in reducing maternal morbidity and mortality worldwide,” says Ralph, who conducted the research while at University of California Berkeley. More research needs to be done to quantify the risks and benefits of providing Depo, and these calculations also have to be adjusted for specific regions and even particular clinics. “One thing to consider is whether women have access to other contraceptive options, whether they will be willing to take up these contraceptive options, and ensuring that women will be comfortable with them,” she says. “I would love to see these findings applied to specific regions. I think that would help women make the most informed decisions.”

TIME medicine

Genetic Testing Company 23andMe Finds New Revenue With Big Pharma

The company’s database of genetic information is worth $10 million to Genentech

The past two years have been a rough and transformative time for the controversial DIY genetic testing company 23andMe. At the end of 2013, the Food and Drug Administration requested that the company shut down its main service, an analysis of a person’s genome gleaned from spit samples that anyone who purchased a kit could send in, noting that interpreting human genes—understanding what changes in DNA mean, and how they contribute or don’t contribute to disease—is still too much of a black box.

But things may be looking better for the company in 2015. On Jan. 6, it announced a $10 million partnership with biotech company Genentech, which will sequence the entire genomes of 3,000 23andMe customers with a higher risk for developing Parkinson’s disease. Genentech is hoping the information will speed development of more effective drugs against the neurodegenerative disorder, in which motor nerves in the brain start to deteriorate. “What attracted us to 23andMe and this opportunity is the work 23andMe has done together with the Michael J. Fox Foundation in the Parkinson’s space,” says Alex Schuth, head of technology innovation and diagnostics for business development at Genentech. “They have built a community of individuals and their family members who have contributed DNA samples. What is unique about this cohort is that it gives us an opportunity to connect clinical data on how patients feel and how their disease is progressing, with their genomic data. That’s unique.” The 23andMe customers will be asked to sign new consent forms as part of any Genentech studies.

MORE Time Out: Behind the FDA’s Decision to Halt Direct to Consumer Genetic Testing

The agreement is one of many that 23andMe CEO and co-founder Anne Wojcicki says are in the works, and hint at the company’s most valuable asset—the genetic information on the 800,000 customers who have sent in their DNA-laden saliva since the company began selling kits in 2006. “Databases, and big data, is suddenly trendy,” says Wojcicki, “especially in health care where people are recognizing that when you have really large numbers, you can learn a lot more. I think we are leading part of that revolution.”

But for the past year, the company hasn’t been sending back health information to customers who pay the $99 for an analysis. Instead, customers are getting reports on their genetic ancestry, with the promise that when the FDA permits it again, they will receive health-related information based on their genetic profile. Wojcicki says that since the FDA action, sales of the kits have been cut by about half, and while they are slowly climbing back up, they haven’t yet reached pre-2013 levels.

Regaining that market is a top priority for 23andMe, says Wojcicki. “Everyone at the company has some kind of role, some involvement, in thinking about the FDA,” she says. “It has transformed the entire company—our product, our execution, how to think about marketing, every aspect of it.” The two entities are exchanging requests and responses, and while she hopes to have a resolution in 2015, it’s not clear yet when the health-related services will be offered.

In the meantime, the genetic information 23andMe has already collected is becoming a potential gold mine for academic researchers and for-profit drug developers. The company has more than 30 agreements with academic researchers for which they receive no monetary compensation, so that scientists can learn more about certain diseases and contribute to basic knowledge about what goes wrong in those conditions. Wojcicki says she’s balancing opportunities with both non-profit and for-profit companies to optimize the value of 23andMe’s database. “Some research has absolutely no monetary capacity, and we should still do those, because fundamentally what 23andMe does is represent the consumer,” she says. “And some research does have monetary capacity, and we should do those too. Because the reality is that the group that is going to develop a drug or treatment or therapy for something like Parkinson’s disease is going to be a for-profit company.”

Read next: These GIFs Show the Freakishly High Definition Future of Body Scanning

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TIME flu

Here’s Where to Find Out If You’re Likely to Get the Flu

It’s not enough to know if your state is a flu hot zone. Now you can find out if the street you live on is teeming with flu cases

With this year’s flu season nearing epidemic levels — it’s widespread in 43 states, according to the Centers for Disease Control and Prevention (CDC) — prevention (and preparation) is certainly your best medicine.

Fortunately, there is no shortage of apps and websites that can help. Flu tracking is a popular subject, and ever since Google Flu Trends launched in 2008, it seems everyone wants to know how prevalent flu is — not just in their state and in their city, but in their neighborhood and even their office building. (Facebook can even help you figure out which of your friends might have given you the flu but tracking members’ posts about the illness and its symptoms.)

And while none are perfect, there are a few good ones.

The CDC’s FluView:

It gathers data from clinics, urgent care centers, doctor’s offices and hospitals and reports the number of people coming in with flu-like symptoms — fever, cough, sore throats, muscle aches — and people who test positive for the bug. It offers a good snapshot but it has some shortcomings. Because it logs symptoms in addition to diagnosed cases, there’s a chance that some of the fever and respiratory problems could be something else entirely. It also doesn’t record the countless people who likely just decide to weather out their illness at home with over-the-counter remedies or some chicken soup. There’s also a lag in the reporting, which means FluView can’t provide a real-time look at what the virus is doing at a given time.

The CDC has an epidemiologist studying alternative ways of collecting flu information, including crowdsourcing, to see if the CDC can provide more real time data. “There is potential there,” says Lynnette Brammer, an epidemiologist in the influenza division at CDC. “But with any data set you’ve got to know how to appropriately interpret that data and when you might be over reaching.”

MORE: Why Some Experts Want Mandatory Flu Shots For School Kids

Flu Near You:

This app is more granular, portraying in real time the actual level of flu activity in a given area. It can pinpoint your location down to the street and give you a low-moderate-high reading on flu activity. It’s based on self reports from people who register on the app and voluntarily provide information on their sniffle status on a weekly basis. Blue dots indicate people who are still symptom-free, while yellow dots indicate people who might have some of the symptoms of flu — including fever, coughs, or sore throats — and red dots represent people who meet the CDC criteria for influenza-like illness: fever over 100F and a cough or sore throat that’s not caused by any other known infection.

Self-reporting may not provide an entirely accurate picture either, however. To address such confounding factors, Flu Near Your deletes the first two reports by newcomers, to reduce the possibility that new users are just playing around with the app, but there’s still no way to verify the symptoms that people log in. But so far, Mark Smolinski, director of global health for Skoll Foundation Global Health Threats, which created the app, is confident that the reports are valid, since they track pretty well with the CDC data.

Alexis de Belloy, who pores over the Flu Near You data, says that registration for the app is up 40% compared to last year, and the proportion of them who actively respond to the weekly surveys is also up; the more participants, the stronger and more reliable the signal generated by the users.

The Flu Forecaster:

Jeffrey Shaman, professor of at the Mailman School of Public Health at Columbia University, decided to combine a bit of both the CDC and real-time strategies into his flu forecaster, which he launched last year. You can select your city and receive a chart of when flu is likely to peak where you live. It’s based on the same predictive modeling that weather forecasters use — combining information from past flu seasons and current trends to make educated guesses about the ebb and flow of cases in the future. “There are problems with all data, so I don’t think any data should be used in isolation,” he says. “We should consider them all until we have that gold standard.”

And it’s not just an academic exercise. Smolinski points out that critical public health information can be gleaned from flu tracking and forecasting, such as how effective a particular flu season’s vaccine is. By comparing rates of illness among people who have been vaccinated and those who haven’t, doctors can get a good sense of whether the shot is a good match for circulating flu strains or not. It can also help doctors, hospitals and pharmacies to make informed decisions about stocking flu remedies like Tamiflu so everyone who needs them will have access to them.

In Australia, crowd-based online surveillance is becoming the country’s go-to resource on flu tracking. Their system, FluTracking.net, asks participants about whether they have had a fever or cough every week during the flu season; since the program began in 2006, more than 16,000 people now complete the survey regularly. In Europe, 10 countries participate in Influenzanet, an online flu tracking system that also relies on volunteers to report on their symptoms weekly.

“It’s what’s coming down the pike, and what’s going to be in our future,” says Shaman of the real time information from the public. “We already get pollution levels and the pollen count. Why not have a real time flu forecast?”

TIME medicine

Why Working at Night Boosts the Risk of Early Death

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Nurses working more night shifts were at higher risk of dying early Image Source—Getty Images

Working while the rest of the world is sleeping may increase your risk of cancer and heart disease

Sleep isn’t just a time to rest and give your body and brain a break. It’s a critical biological function that restores and replenishes important body systems. Now, yet another study on shift workers shows that their unusual hours may be cutting their lives short—and that’s especially true for those who have rotating night shifts, rather than permanent graveyard duty.

In a study published in the American Journal of Preventive Medicine, scientists led by Dr. Eva Schernhammer, an epidemiologist at Brigham and Women’s Hospital, studied 74,862 nurses enrolled in the Nurses’ Health Study since 1976. The nurses were an ideal group for studying the effects of rotating night shifts on the body, since RNs tend to have changing night shift obligations over an average month rather than set schedules.

MORE: The Power of Sleep

After 22 years, researchers found that the women who worked on rotating night shifts for more than five years were up to 11% more likely to have died early compared to those who never worked these shifts. In fact, those working for more than 15 years on rotating night shifts had a 38% higher risk of dying from heart disease than nurses who only worked during the day. Surprisingly, rotating night shifts were also linked to a 25% higher risk of dying from lung cancer and 33% greater risk of colon cancer death. The increased risk of lung cancer could be attributed to a higher rate of smoking among night shift workers, says Schernhammer.

The population of nurses with the longest rotating night shifts also shared risk factors that endangered their health: they were heavier on average than their day-working counterparts, more likely to smoke and have high blood pressure, and more likely to have diabetes and elevated cholesterol. But the connection between more rotating night shift hours and higher death rates remained strong after the scientists adjusted for them.

MORE: Why You Shouldn’t Read a Tablet Before Bed

The data support the idea that changing the body’s natural rhythms by being active at night and asleep during the day may have harmful consequences, especially if you shift this rhythm inconsistently. “It’s sort of like flying between London and New York every three days — constant jet lag,” says Schernhammer. “However, if you fly from London to New York and stay in New York, then jet lag would subside after a few days, and that’s what we assume happens in permanent night workers.”

Why does the body react when sleep cycles change? Previous studies showed that too little sleep or the kind that’s disrupted can alter melatonin levels so that the body never powers down and slips into restorative mode, a time when much-needed repairs are made to cells and tissues and supplies of nutrients are replenished to the body. Without this period of rest, important processes such as inflammation, fat and sugar metabolism and immune functions get out of balance, creating fertile ground for heart disease or cancer. The growing number of studies connecting shift work with unhealthy outcomes led the World Health Organization to classify shift work as a probable carcinogen in 2007.

MORE: These 6 Things Will Bring You a Great Night’s Sleep

Schernhammer and her colleagues show that the categorization may have merit, but not everyone can avoid night shift work. Researchers are studying how these people might counteract some of the effects of their unusual work hours, but none of these strategies, including light lamps and sleep aids, has so far been proven to help. In the meantime, she says that shift workers concerned about their risk should do everything they can to lower their risk of heart and cancer risk in other ways — by quitting smoking, getting enough exercise, eating a healthy diet and getting regular cancer screenings. “Hopefully in the near future we can also recommend additional measures that alleviate some of the strain that night work imposes on the circadian system,” she says, “by matching their shift schedules, to the extent possible, with their inherent sleep preferences — whether they are night owls or morning types.”

TIME Cancer

Your Chances of Surviving Cancer May Depend on Where You Live

Cancer deaths across the country have been dropping, but some states are doing better than others

In its annual report on cancer rates and deaths, the American Cancer Society (ACS) reports that deaths from cancer have dropped by 22% over the past 20 years, saving 1.5 million lives.

The review, published in the journal CA: A Cancer Journal for Clinicians, included data from 2007 to 2011 and found that decreases in deaths from four major cancers—lung, breast, prostate and colon—are driving much of the improvement. More widespread screening, which is leading to early detection and treatment, is helping to find more cancers and manage them before they become fatal, says Rebecca Siegel, director of surveillance information for the ACS and lead author of the study. Deaths from prostate and colon cancers have dropped by almost half since their peak several years ago, and lung and breast cancer have declined by about a third from their highest rates.

But the data also show a disturbing trend of slower progress in southern states. On average, death rates in the lower part of the U.S. have declined by about 15%, compared to drops of 25% to 30% in Delaware, Maryland, Massachusetts and New York.

The reason for the smaller declines, says Siegel, may have a lot to do with higher smoking rates in states like South Carolina and Kentucky, as well as more obesity and greater disparities in socioeconomic status. People with lower incomes are less likely to have access to cancer screening and treatment programs. “We are seeing large differences by state,” she says. “We need to reach everyone in the population with advances in early detection and improvements in treatment because they just aren’t equally disseminated. That’s why you see differences; it’s not just biology.”

The improvements in northeastern states shows that it’s possible. “If we could apply everything we know to everyone in the U.S., there would be enormous gains from just that,” says Siegel.

That’s especially important as the population continues to age. Since cancer is generally a disease of aging, the absolute number of cancer diagnoses, and potentially deaths, could increase. (In 2015, an estimated 589,430 Americans will die of cancer.) But expanding screening programs and ensuring that more people have access to them could help keep cancer rates and deaths trending downward.

Read next: Most Cancer Is Beyond Your Control, Breakthrough Study Finds

TIME Cancer

Most Cancer Is Beyond Your Control, Breakthrough Study Finds

There’s a lot we can do to protect ourselves from certain cancers — don’t smoke, avoid prolonged exposure to the sun, and try not to breathe or ingest too many chemical pollutants in the air or our food. But scientists have always known that this was only part of the cancer story. There’s also heredity, but that only explains about 5% to 10% of cancer. The truth of the matter is that some tumors emerge simply at random. But how much of malignancy can be attributed to this unfortunate roll of the dice? What really causes cancer?

Christian Tomasetti and Bert Vogelstein at Johns Hopkins University believe they may have found an answer, and it’s likely to turn our understanding of cancer — and how it should be diagnosed and treated — on its head. In a groundbreaking paper published in Science, the duo describe a new factor, a tissue’s stem cells, that may explain as much as two-thirds of the difference in cancer risk among different tissues.

Many tissues in the body have stem cells that serve as factories for churning out more cells of the same kind; it’s what keeps our skin cells refreshed, and our blood and immune cells young and vigorous. This replicative power is the engine that keeps the body going, allowing tissues to replace cells as they die off. But it’s also the process behind cancer, since cancer is caused by cells that pick up mutations in their DNA when they divide — and stem cells are the only population that copy their DNA and divide to make more cells. Only a small proportion of a tissue’s cells are made up of stem cells, so Tomasetti and Vogelstein decided to map out whether the number of stem cells in a specific tissue bears any relationship to its tendency to develop cancer.

MORE Promising New Cancer Treatment Uses Immune Cells

Indeed, when they charted out the stem cell data for 31 types of tissues, they found a dramatic connection between the two — the more stem cells the tissue had, the higher its incidence of cancer over a person’s life time on average. “Think of cancer as the risk of having an accident if you are driving a car,” says Tomasetti, a biostatistician who holds positions in the department of oncology at Johns Hopkins Kimmel Cancer Center and the Johns Hopkins Bloomberg School of Public Health. “If you drive the car on a cross country trip, your risk of an accident is much higher than if you take a local trip to the grocery store. The risk correlates to the length of the trip. The trip to the grocery store might be thought of as bone cancer, which has few stem cell divisions. While the cross country trip might be more like colon cancer, which has many more cell divisions.”

In fact, the correlation held strong among cancers that were both common and more rare. The more likely those cells would divide and develop DNA errors or mutations in the process that led to uncontrolled growth, the more likely that tissue would develop tumors.

“It was quite surprising to us. We think it’s pretty big,” he says. “About 65% of cancer incidence across tissue types appears to be explained by the number of stem cell divisions.”

MORE Stem Cells That Kill

Having a detailed understanding of both how large a tissue’s stem cell population is, as well as how active it is, could be a determining factor in whether it’s likely to develop cancer. Both the brain cells that can cause glioblastoma and medulloblastoma, and the colon contain about the same number of stem cells, Tomasetti estimates — about one hundred million. But the colon stem cells divide about 6000 times on average during lifetime, compared to nearly zero for the brain stem cells. That leads to rates of colon cancer that are 22 times higher than rates of the brain tumors.

PrintCredit: C. Tomasetti, B. Vogelstein and illustrator Elizabeth Cook, Johns Hopkins

Such an explanation could also resolve some of cancer’s mysteries — why people who don’t smoke still get lung cancer in surprising numbers, or why rates of colon cancer are higher than rates of cancer in the small intestine, despite being shorter in length. One reason, says Tomasetti, could have to do with the different stem cell activity in these tissues.

This finding potentially changes the landscape of cancer. In recent decades, cancer rates have come down due to aggressive efforts to educate and motivate people to take positive steps toward preventing cancer in the first place, such as quitting smoking and avoiding the sun’s ultraviolet rays. Have those messages been wrong?

Not exactly. Tomasetti says that the study shows that it’s time to redirect that cancer strategy a bit — not abandon it. For example, he and Vogelstein propose looking at cancers in two categories, those that are primarily due to genetic bad luck, and those that are due to that unfortunate roll of the genetic dice plus environmental or hereditary factors. So melanoma, ovarian cancer, many brain cancers, lung cancer among non-smokers, the most common leukemias and bone cancers, for example, are pretty much out of people’s control. They’re the result of the random mutations caused by the stem cells dividing in these tissues — bone, blood, ovaries, brain and skin — that make mistakes that turn malignant. For these cancers, changing your lifestyle or trying other interventions to stop the cancer from occurring in the first place won’t help. But being vigilant about screening, and picking up the first signs of trouble early, can be life saving.

MORE This New Kind of Stem Cell May Revolutionize How We Treat Diseases

For the other type of cancers, those that are the product of both stem cell mutations and heredity or other exposures, continuing with proven prevention methods, which include screening in cases of inherited disease, as well as quitting smoking and reducing exposure to radiation and carcinogens, is still critical. That’s what has lowered rates of lung cancer among smokers, for example, and colon cancer among those with hereditary disease.

“Everything we know about altering lifestyles to prevent cancer from the environmental point of view we absolutely need to continue doing,” says Tomasetti. “If anything it puts more stress on the need to spend even more money on early detection. It may be the key tool for quite a few cancer types.”

Tomasetti admits that two common cancers are missing from the study — breast cancer and prostate cancer. That’s because knowledge about their stem cell populations, and how often those tissues renew, isn’t quite as solid as it is for tissues such as colon. “We are working on that,” he says. “We hope this type of work highlighting the importance of self renewal will cause others to investigate these stem cell populations in more detail as well.”

In the meantime, he stresses that while we may not be able to prevent the tumors from forming, it’s still possible to treat them and potentially save lives by finding them early and removing them or using chemotherapy or radiation to keep them under control. “My biggest fear is that people will say forget about it, and then do nothing. The opposite is true. We need to do everything we did before, but we want to do it even more than before,” he says.

Read next: Your Chances of Surviving Cancer May Depend on Where You Live

TIME Obesity

Weight Loss Supplements Don’t Work for Most People, Study Finds

A Consumer Reports survey shows that most people who use weight loss supplements aren’t aware of how potentially unsafe or ineffective they are

In a survey of 3,000 Americans, researchers at Consumer Reports report Tuesday that most are confused about how weight loss supplements make it to market, and that means they aren’t fully informed about how safe or effective the pills are. What’s more, of those Americans who have tried such pills to lose weight, very few met—and maintained—their goal.

About 20% of those who use diet supplements to lose weight believed they were safe and tested by the Food and Drug Administration. But unlike prescription drugs, supplements aren’t regulated under the strict criteria that require manufacturers to perform rigorous safety and effectiveness testing before getting approved. Instead, supplements are regulated more like foods, so they are assumed to be safe unless they’re shown not to be by reports from users.

Meanwhile, roughly 20% of those surveyed believed that the supplements were safer than more stringently regulated prescription drugs because they were “natural.” But recent studies revealed that many supplements contain substances that have been banned because of safety concerns; in one study two-thirds of weight loss supplements contained banned ingredients. And the supplements aren’t always benign. About half of users reported at least one side effect, ranging from dry mouth to more serious digestive issues including diarrhea and constipation, as well as rapid heart rate.

When it comes to actually losing weight, the supplements didn’t fare so well either. A third didn’t shed any pounds at all, and only 9% of the respondents said they lost their target weight and were able to keep it off. But the supplements may not even take all of the credit for that success — 85% of the people who lost weight while taking a supplement also changed their diet and had an exercise plan.

Which goes back to the advice that most doctors give to anyone serious about getting slimmer: weight loss doesn’t come in a pill, it comes with a healthy diet and regular exercise program.

TIME medicine

The Surest Way to Cure Your Hangover

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The holidays. A new year. There’s a lot to celebrate, so don’t ruin it with a hangover or a food coma. Here's how to avoid both

A night of too much booze often comes with a side of queasiness and a pounding headache. We’ve all heard rumors about what helps, from hot sauce to burnt toast to more alcohol, but here’s what doctors say really works as a morning-after remedy.

First, it’s important to recognize what your hungover body is trying to tell you. Alcohol makes you urinate more, and that depletes your body of much-needed fluids. At the same time, impurities in the fermenting alcohol essentially flood your body with toxins, causing those painful side effects.

It’s not always easy in practice, but the best way to avoid that nasty hangover in the first place is to alternate your alcoholic drinks with water.

Too late for that? On the morning after, the very best way to ease your stomach is to drink water. Water will rehydrate you, dilute the toxins that have built up overnight and flush them out.

Eating is also key, whether you want to fight or prevent a hangover. Filling your stomach before you drink, especially with heavier, greasier foods, can line the stomach and slow down the absorption of alcohol. And noshing after a night out, even if it’s last thing you feel like doing, can replenish your body with nutrients so it starts to function better.

READ MORE Should You Eat Whatever You Want For The Holidays?

If you remember, try taking two aspirin before going to bed, and another couple when you wake up. That can ease some of the head pounding that comes from the drop in blood alcohol and being dehydrated from all that drinking.

As for overeating, it’s sometimes inevitable, especially at holiday feasts. Try to cut down on your portions, or at least eat more slowly. That can help your brain and body stay in sync and work together to determine when you’re no longer hungry. Extra points if you load up on high-fiber foods like whole grains, vegetables and nuts; they’ll make you evacuate your bowels more frequently and make you feel less uncomfortable. Just remember not to bring it up during one of those big meals.

TIME

Why You Shouldn’t Read a Tablet Before Bed

If reading is your way of easing into sleep, pick up a printed book instead of a digital one

There’s nothing wrong with settling down with a good book at the end of day to melt away tension and help you to unwind. But if you’re picking up an e-reader or a tablet, then you’re doing it all wrong.

That’s what Anne-Marie Chang, associate professor of biobehavioral health at Penn State University, and her colleagues found when they compared digital readers with the printed word. Reporting in the Proceedings of the National Academy of Sciences, they say that people who use the electronic devices such as an iPad had more disrupted sleep patterns and were more tired the next morning than those who read from traditional books.

Chang, who conducted the study while at Brigham and Women’s Hospital, designed the trial to be as objective as possible. What Chang found was a marked difference between each participant’s sleep patterns and alertness depending on whether they read from a digital reader or from a book. When they read from an iPad, their evening levels of melatonin failed to drop as much as they should, while they remained at expected levels when they read from a book. That led to a delay in body’s biological signal to go so sleep of about an hour and a half, making the participants more alert and therefore not ready for bed.

And when the scientists looked at their sleep patterns, they found that the differences went even deeper. When the volunteers read from electronic devices, they had shorter REM sleep, the stage in which memories are consolidated and the brain refreshes itself, than when they read from printed books. This occurred even though the volunteers slept for the same amount of time, eight hours, every night.

MORE: 3 Reasons To Keep Your Phone Away from the Bed

What’s more, the effect of those differences in sleep patterns spilled over into the next morning. When they read from digital readers, the participants reported feeling sleepier and were less alert (as measured on standardized testing of alertness) than when they used books. “What was surprising to me was that we would see effects the next day. There was no difference in total sleep duration between the two conditions, but there was a significant amount of REM sleep difference,” says Chang. “This may indicate that these effects are longer term than we thought.”

Previous studies showed that one reason for the disrupted sleep linked to the electronic devices may be due to the type of light they use. It’s in the blue wavelength, and some researchers have connected this light to a disruptions in the melatonin system, similar to those Chang found in the study. She says it’s also possible that having the light shine directly into the eyes, as backlit electronic readers do, may also keep the body’s sleep signals from activating — reading lamps or room lights reflect light so aren’t as disruptive to the body’s wake-sleep cycle.

The findings hint at why sleep — getting enough, and getting good quality sleep — is becoming more a of challenge and potentially a growing health problem. “There is an easy answer but it’s not a popular one that’s easy to hear,” says Chang. “Using electronic devices is not a train that is slowing down any time soon. So the important thing is to know more about them, and how they are affecting our lives, our health and our well being.” And in the meantime, maybe put the tablet down in the hours before you go to bed. Or buy a book.

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TIME

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