A series of studies testing different scenarios (called simulations by the study authors) were carried out using incidence data from the Nordic countries to determine the likelihood of detecting various levels of risk as reported in studies of cell phone use and brain tumors between 1979 and 2008. The results were compatible with no increased risks from cell phones, as reported by most epidemiologic studies. The findings did suggest that the increase reported among the subset of heaviest regular users in the Interphone study could not be ruled out but was unlikely. The highly increased risks reported in the Swedish pooled analysis were strongly inconsistent with the observed glioma rates in the Nordic countries (24).
The reason we’re talking about cellphones and cancer — why there’s a concern here — is because they emit radiation, the invisible waves of electric and magnetic energy, of varying power, organized on the electromagnetic spectrum. You can see in the graphic below that less powerful (or lower-frequency) types of radiation are on the left, moving to the more powerful (or higher-frequency) types of radiation on the right.

Information and statements made are for education purposes and are not intended to replace the advice of your treating doctor. Global Healing Center does not dispense medical advice, prescribe, or diagnose illness. The views and nutritional advice expressed by Global Healing Center are not intended to be a substitute for conventional medical service. If you have a severe medical condition or health concern, see your physician. This Web site contains links to Web sites operated by other parties. Such links are provided for your convenience and reference only. We are not responsible for the content or products of any linked site or any link contained in a linked site. Global Healing Center does not adopt any medical claims which may have been made in 3rd party references. Where Global Healing Center has control over the posting or other communications of such claims to the public, Global Healing Center will make its best effort to remove such claims.
The next day, telecommunications stocks took a big hit on Wall Street and the media had a field day. The industry trade association at the time, the Telecommunications Industry Association (TIA), went into crisis mode, claiming thousands of studies proved cell phones were safe and what Reynard and his attorney said was bunk. TIA reassured the public that the government had approved cell phones, so that meant they were safe. The media demanded to see the studies, but, says Dr. Carlo, “The industry had lied. The only studies in existence then were on microwave ovens. At that time, 15 million people were using cell phones, a product that had never been tested for safety.”
Independently tested DefenderShield technology uses a patent-pending sophisticated layering of separate non-toxic, human safe materials processed for maximum radiation blocking efficiency. Each material has unique and targeted radiation shielding characteristics designed to work in unison to up to eliminate all radiation emissions from 0 to 10 GHz.
But the results of these two rat studies align with those of the biggest cell phone-radiation human study to date, INTERPHONE. The INTERPHONE study, published in 2011, was a coordinated effort by researchers at 16 institutions across 13 countries, and found that the heaviest mobile phone users were more likely to develop glioma—the same type of brain cancer the NTP study found in the male rats. “So there’s a concordance between the animal and human data,” Melnick says.

"For example," Johnson said, "what does a fractal like pattern have to do with a hologram? The answer is, of course, nothing that is apparent. Then there is a truly convoluted assertion that cell phones can be instrumental in ‘psychoemotional' effects on humans because of their lower-frequency outputs. This too, is gibberish. In short, this is technobabble that will potentially snow someone who has no science background."
A full featured desktop or wall mount corded telephone (no microwaves) combined with a special ultra low EMF headset. You get all the benefits of a normal telephone without putting yourself close to the strong magnetic fields associated with the handset, speakerphone, or phone base. The special headset cord is about 3 feet long and uses a plastic tube to carry the sound to your ear. Absolutely no electronics, wires or magnets are near your ear. Cord provides distance from telephone base and traditional handset, convenient mobility, and can be extended up to 15 feet with option extension cord, sold separately (see below). Tested and approved by Less EMF Inc., dramatic field reduction when the headset is used. Although pictured as white, our current stock is a black phone.
SafeSleeve was founded in California by two Engineering graduates (University of Cal Poly San Luis Obispo) Cary and Alaey, with a desire to make a difference. They wanted to develop a product to help simplify, protect, and enhance the lives of their increasingly busy, tech dependent peers, family and friends. This is apparent in the highly efficient and useful, yet stylish designs and branding of SafeSleeve products. 
5. Use an EMF shielding device. A variety of holsters and other cell phone holders and shields are available that claim to block radiation. If you buy such a product, look to see if it has an SAR (specific absorption rate) value. You want a shielding device that blocks the majority of EMFs. (SAR is a measure of the rate at which energy is absorbed by a body exposed to EMFs.) 
I'm glad I spent the money to get this protection. Again, I consider this an "insurance policy" and hope cell phone radiation is over hyped. However, mounting evidence seems to indicate otherwise, so I feel more comfortable knowing I'm taking proactive steps to protect against a possible health problem I and my family might face in the future from long and close exposure to cell phones close to the body and head.

A recent small study in people has shown that cell phones may also have some other effects on the brain, although it’s not clear if they’re harmful. The study found that when people had an active cell phone held up to their ear for 50 minutes, brain tissues on the same side of the head as the phone used more glucose than did tissues on the other side of the brain. Glucose is a sugar that normally serves as the brain’s fuel. Glucose use goes up in certain parts of the brain when it is in use, such as when we are thinking, speaking, or moving. The possible health effect, if any, from the increase in glucose use from cell phone energy is unknown.


That brings us back to the main question here: Do cellphones cause tumors? We chose to focus this story on cancer risk, since it seems like the most common health concern people have about cellphones. But before we get to the answers, we need to take another (brief) detour to explain how this science has been done with human subjects. To do that, we need to zoom in on a nerdy subject: research methods.
As in the NTP study, Ramazzini investigators detected statistically elevated rates of heart schwannomas in male rats at the highest dose. They also had weaker findings linking RF exposure to cancer of glial cells in the brain, which were limited to females. Ronald Melnick, a retired NTP toxicologist who designed the NTP study, says a measure of consistency between the two studies is important, because “reproducibility in science increases our confidence in the observed results.”
A third requirement was for the FDA to create a formal interagency working group to oversee the work and provide input. The purpose of this was to alleviate any perception that the industry was paying for a result, not for the research itself. But the fourth and last requirement was considered by Dr. Carlo to be highly critical: “Everything needed to be done in sunlight. The media had to have access to everything we did.”
Still, despite the odds, these fears could be around for a while — because it’s hard to prove that cellphone radiation doesn’t cause harm. There are just too many combinations of genes, environmental exposures, patterns of cellphone use, plus a healthy helping of random chance to consider. It’s why we’re still having the conversation about whether coffee, for example, is good or bad for us. So while the bulk of evidence points to no health effects from cellphone radiation, the scientific literature is still somewhat mixed, Foster says. “Someone who wants to worry can pick and choose and find a lot of evidence that would support their theories.”
Cell phones work by sending signals to (and receiving them from) nearby cell towers (base stations) using RF waves. This is a form of electromagnetic energy that falls between FM radio waves and microwaves. Like FM radio waves, microwaves, visible light, and heat, RF waves are a form of non-ionizing radiation. They don’t have enough energy to cause cancer by directly damaging the DNA inside cells. RF waves are different from stronger (ionizing) types of radiation such as x-rays, gamma rays, and ultraviolet (UV) light, which can break the chemical bonds in DNA.

It isn’t just cell phones. When you get the phantom twitch, it is not from a nervous system reaction to the phone vibrator as many suggest. Why do I say that? One, I rarely experience phone vibration, yet I get the phantom twitch. Two, as I have to use a rental car for work and they always give you two electronic keys (they do NOT vibrate), that is in my pocket with my own car key, bringing the total of non-vibrating keys to three. They do not vibrate, but I still get the phantom twitch.


The government’s policies must change. Cell phone users should make their voices heard to prompt the FCC and manufacturers of cell phones and cases to ensure that these accessories never increase and, to the extent possible, decrease, users’ radiation exposure. At minimum, the FCC must take cell phone cases into consideration when it updates its standards to ensure that the use of a case will not expose people to more radiation than its legal SAR limit.  
A recent small study in people has shown that cell phones may also have some other effects on the brain, although it’s not clear if they’re harmful. The study found that when people had an active cell phone held up to their ear for 50 minutes, brain tissues on the same side of the head as the phone used more glucose than did tissues on the other side of the brain. Glucose is a sugar that normally serves as the brain’s fuel. Glucose use goes up in certain parts of the brain when it is in use, such as when we are thinking, speaking, or moving. The possible health effect, if any, from the increase in glucose use from cell phone energy is unknown.
Don’t rely on a “radiation shield” or other products claiming to block RF energy, electromagnetic fields, or radiation from cell phones. According to the U.S. Federal Trade Commission, products that interfere with the phone’s signal may force it to work harder and emit more RF energy in order to stay connected, possibly increasing your exposure. It is best to use wired solutions to reduce RF rather than rely on an untested  product.
Third, most of the studies published so far have focused on adults, rather than children. (One case-control study looking at children and teens did not find a significant link to brain tumors, but the small size of the study limited its power to detect modest risks.) Cell phone use is now widespread even among younger children. It is possible that if there are health effects, they might be more pronounced in children because their bodies might be more sensitive to RF energy. Another concern is that children’s lifetime exposure to the energy from cell phones will be greater than adults’, who started using them at a later age.
Transmitters, including cell phones, emit radio signals on more than the assigned frequency. These other signals on other frequencies are “harmonics” and/or “noise” and/or “dirty” signals from less than optimal transmitters, antennae, and/or resonating frequencies emitted from metallic objects in close proximity to the transmitter, like the other components of the cell phone.
The government, however, does not require phone manufacturers to consider the effect of cases when they conduct compliance tests to meet the FCC’s allowable radiation exposure limits. The significance of this omission was underscored by tests commissioned by case-maker Pong Research and submitted to the FCC in May 2012. Those tests showed that three models of cases made by competing companies and used with an iPhone4 increased the phones’ Specific Absorption Rate, or SAR – the amount of radiation absorbed by the user’s body – by 20-to-70 percent (Table 1).
But, like the human studies, one can pick apart the NTP studies too. For one thing, the animals experienced cell phone radiation that was different from what humans live with. As Bucher said in a statement, “In our studies, rats and mice received radio frequency radiation across their whole bodies. By contrast, people are mostly exposed in specific local tissues close to where they hold the phone. In addition, the exposure levels and durations in our studies were greater than what people experience.”
The three most common brain tumor types — and the ones most cellphone and human health studies focused on — are gliomas (malignant tumors of the brain and spinal cord), meningiomas (mostly noncancerous tumors of the membranes surrounding the brain and spinal cord, though a small percentage are cancerous), and acoustic neuromas (noncancerous tumors on the main nerve that leads from the inner ear to the brain). Note that of these, gliomas are the main concern — they generally have more severe outcomes than meningiomas and acoustic neuromas.
I'm glad I spent the money to get this protection. Again, I consider this an "insurance policy" and hope cell phone radiation is over hyped. However, mounting evidence seems to indicate otherwise, so I feel more comfortable knowing I'm taking proactive steps to protect against a possible health problem I and my family might face in the future from long and close exposure to cell phones close to the body and head.
The researchers found other strange effects that muddied the interpretation of the studies: The rats exposed to cellphones seemed to outlive the rats in the control group, for example. There was no clear linear relationship between higher levels of cellphone exposure and more cancer at some tissue sites, and the cancer rate in the control group was lower than it should have been at other tissue sites.
This is why it’s important to always use either your phone’s speakerphone or an appropriate wired earpiece whenever possible, avoiding direct contact between your phone and your ear or hand. The best earpieces are those equipped with hollow tubing between the antenna in the wire and the earpiece, as these help maximize the distance between the radiation-emitting antenna and your head.
Compatible Phone Models iPhone, Samsung, Motorola and more, This device is designed to work with all cell phones, All dodels, Smart Phones, Flip Phones Apple iPhone 8, Apple iPhone 7, Apple iPhone 6, Apple iPhone 8, 7, 6, Apple iPhone 8, iPhone 7, iPhone 6 iPhone 6 Plus, iPhone 6S Plus, iPhone 7 Plus, iPhone 8 Plus iPhone 6, iPhone 6S, iPhone 7, iPhone 8
Using the gauss meter at varied locations, you can easily detect electromagnetic radiation “hot spots” where exposure to these ominous frequencies is the greatest. Armed with this crucial information, you can then avoid these areas, re-arranging furniture or electronic devices as needed in order to avoid unnecessary exposure to electromagnetic radiation.
SafeSleeve for the iPhone 6 and 6s is the industry leading cell phone radiation protector. Our anti-radiation shielding technology has been tested in an FCC certified lab to block over 99% of RF radiation and over 92% of ELF radiation. Simply open the flap to answer, and re-close when speaking to be protected from potentially harmful radiation. The technology will also block radiation when storing in your pocket, just position the front flap to face your body. Rugged and double protective case includes an inner silicone shell to hold your phone in place and a reinforced outer case with magnetic latch to hold it closed. Convenient built-in cell phone case wallet allows you to carry up to 4 cards and/or cash with RFID protection. Leave the bulky wallet at home and carry everything in one lightweight package. Enjoy the peace of mind of knowing you are protected by lab tested shielding technology with the added convenience of a built in case, RFID blocker wallet and stand!

As a rule, modern medical equipment is well protected against exposure to radiowave radiation. Therefore, there is generally no need for concern regarding the effects of mobile phones on the normal function of the equipment. Nevertheless, the Ministry of Health recommends not to have a mobile phone in the immediate proximity (a distance of 30-50 cm from the portable medical equipment or from medical equipment implanted in the patient's body).
Nice quality vinyl bumper sticker is a not-so-gentle reminder to fellow motorists of the one of the many dangers of cellphone use: distraction! If you ever get the chance, you can also explain the other hazards as well: reaction time, increased permeability of the blood-brain barrier, and possibly brain tumors. Good for cars, trucks, bikes, skates and just about any other moving vehicle.

There are ongoing worries about whether cellphones can give you cancer — especially brain cancer, since our phones spend so much time near our faces. It’s true that cell phones do emit radiation. But it’s radiofrequency radiation, which is much lower energy than the ionizing radiation you’d get from an X-ray, or, say, nuclear fallout. Ionizing radiation can cause DNA damage that can eventually lead to cancer. But the radiofrequency radiation from a cellphone doesn’t work that way — and today’s results support that.
I liked the way Blocsock implemented this protection and the quality of the product construction, combined with the validated test results, so I recently ordered ones for the rest of my family. I think Blocsock is the BMW-class of what I could find for products that protect against cell phone radiation. My wife has a larger Droid phone and it fits in the case (just barely though)! I hope the makers consider making a larger model for all the new, larger smartphones that recently came out with the larger screen sizes. Again, check to make sure your phone fits, which a friendly message to the company will answer if you are not sure.
People can also reduce their exposure by limiting cell-phone use when the cellular signal is weak; when traveling in a high-speed car, bus or train; to stream audio or video; or to download or upload large files. All of these circumstances cause phones to put out higher-than-normal levels of RF energy. Phones also emit RF energy when connected to WiFi or Bluetooth devices, but at lower levels.

Dr. Carlo and his team developed new exposure systems that could mimic head-only exposure to EMR in people, as those were the only systems that could approximate what really happened with cell phone exposure. Those exposure systems were then used for both in vitro (laboratory) and in vivo (animal) studies. The in vitro studies used human blood and lymph tissue in test tubes and petri dishes that were exposed to EMR. These studies identified the micronuclei in human blood, for example, associated with cell phone near-field radiation. The in vivo studies used head only exposure systems and laboratory rats. These studies identified DNA damage and other genetic markers.


The only sure way is to stop using a cell phone. Most people however would prefer to play safe by simply reducing their exposure to radio frequency radiation. Bluetooth devices emit only 10% of the radiation of a cell phone. A hands-free set enables the user to keep the phone away from the head but usually leaves the phone near some other part of the body. It is safe to say that in the event that radio frequency radiation causes damage, you would like to protect other parts of your body. Therefore the only way to reduce your risk is to reduce the radio frequency radiation your body absorbs. SAR Shield reduces radio frequency radiation by up to 89%. 

None of the three cases contain metallic parts, which are known to affect SAR, but all increased the user’s radiation exposure. The effect on radiation exposure would likely vary with each of the hundreds of cases on the market, and each would have to be tested individually to come up with an exact measure. The results in Table 1, however, are believed to reflect the range of radiation increases.
I noticed the Blocsock hardly added any bulk to my phone, and fit comfortably in my pocket. I have a Rocketfish RF-MTVT2SP protective gel case and thankfully the phone fits the Blocsock without having to take off this case. The Blocsock is very easy to use, and is quick and easy to take out and answer the phone. Again, if you get one, make sure the size you order is right and not too tight or loose. The pouch on the Blocsock is handy when using the phone to call people so the phone can be placed in the pouch between the Blocsock and me, protecting my head from radiation while still enabling people to clearly hear me and vice versa.
Forced to take action, the cell phone industry set up a non-profit organization, Wireless Technology Research (WTR), to perform the study. Dr. Carlo developed the program outline and was asked to head the research. Oversight of the issue was charged to the FDA, though it could have and probably should have gone to the Environmental Protection Agency (EPA), which fought hard for jurisdiction. But the industry had enough influence in Washington to get whatever overseer it wanted. It simply didn’t want to tangle with EPA because, says Dr. Carlo, “… the EPA is tough.”
✅ PROTECT YOUR HEAD & BODY FROM RADIATION: It is scientifically proven that it’s best to keep your phone away from your body because the radiation exposure often exceeds FCC regulations. That’s why our emf protection cell phone radiation shield will immediately negate symptoms such as headaches, dizziness, memory loss, anxiety, fatigue and much more.
The most common effect is heat generation (though non-thermal biological harm has also been demonstrated), which can alter the characteristics of various bodily tissues depending on the amount of radiation present and its ability to penetrate the body. Tissue damage can promote the cellular mutations and increase your long-term risk of developing cancer.
The study specifically used 2G and 3G frequencies — not the frequencies used on more advanced 4G or 5G networks. Researchers exposed the rodents’ entire bodies to the radiowaves for more than nine hours per day, for up to two years. (“A rat that is 2 years old is roughly equivalent to a 70-year-old person,” STAT News reports.) These exposure levels were much higher than what people would experience, John Bucher, senior scientist with the NTP, says in a statement. “So, these findings should not be directly extrapolated to human cell phone usage,” he says.
Since speaking with Samet, further details came out from a large study that beamed high levels of phone radiation at rats and mice. While there remain quirks in the findings, the latest evidence still doesn’t find a link between phone radiation and cancer. In response, the FDA said, “Taken together, all of this research ... [has] given us the confidence that the current safety limits for cell phone radiation remain acceptable for protecting the public health.”
So what do you do when you need a wireless radiation emitting device but you want to limit the exposure to the people? Perhaps you use a wireless baby monitor, have a cordless phone base station, or you sleep with your cell phone on your nightstand. Maybe there is a wifi router right next to you at work or school. RadiaFence is the answer. It’s a free-standing, semi-transparent microwave barrier that you can put almost anywhere you need. It blocks most of the radiation emitted in one direction by “casting a shadow” (typically 70-90% reduction), while still allowing the wireless device to work. Like sitting in the shade on a sunny day. Portable, inexpensive, attractive. And it couldn’t be easier to use. If you like, you can add a decorative photo or warning sign to change the appearance. Available in 5 styles. Pick the sizes which meet your needs. Style may differ from images.
Considering the current standards in the State of Israel and due to the distance from the base stations, the radiation that reaches people from this source is extremely low. Although direct studies that will test the effects of antennas on human health are not feasible, considering the aforesaid, this probably does not pose a significant health risk.
In fact, nobody can really explain how exactly cellphone radiation could cause cancer, says Christopher Labos, a cardiologist and biostatistician at McGill University. “You don’t necessarily have to understand how something works to prove that it’s dangerous, but it would certainly make the case more compelling,” says Labos, who wrote a detailed analysis for Science-Based Medicine about the recent government cellphone radiation study.
To find out about the state of research on the link between phones and cancer, we spoke with Jonathan Samet, dean of the Colorado School of Public Health and an expert in phone radiation who led a World Health Organization working group on the subject. In 2011, the WHO group deemed phone radiation “possibly carcinogenic,” which is less certain than other classifications, but isn’t an outright “no” either. Six years later, Samet said the evidence in either direction is still mixed and that for the time being, there remains “some indication” of risk.
Radiation is all around us. Power lines, appliances, and electronic devices all emit electromagnetic frequencies. One source that many of us keep close, perhaps too close, are cell phones, tablets, and other mobile devices. They all use radio frequency (RF) electromagnetic energy, a form of non-ionizing radiation, to communicate. Research has shown that this type of radiation is not benign or harmless to the human body, especially children. Exposure to cell phone and Wifi radiation has been linked to fatigue, dizziness, mental fog, and even worse. As a result, the demand for products that reduce exposure to device radiation is on the rise. In fact, "How can I protect myself from cell phone radiation? What do you recommend?" is a question we get all the time. So, to help, I wanted to offer my thoughts on five products I've found that I believe are worth a look if you're interested in reducing your exposure to cell phone and mobile device radiation.
A large, long-term study has been comparing all of the people in Denmark who had a cell phone subscription between 1982 and 1995 (about 400,000 people) to those without a subscription to look for a possible increase in brain tumors. The most recent update of the study followed people through 2007. Cell phone use, even for more than 13 years, was not linked with an increased risk of brain tumors, salivary gland tumors, or cancer overall, nor was there a link with any brain tumor subtypes or with tumors in any location within the brain.
Specific Absorption Rate (SAR) is an indicator for calculating the level of radiation absorbed in the body. This indicator represents the rate of energy absorption by the tissue and is expressed in units of Watt/kg. The Consumer Protection Regulations (information on non-ionizing radiation from mobile phones) of 2002, stipulate the duty to label the product, specifying the radiation level of the phone’s model and the maximum permitted radiation level. This regulation allows to compare the emitted radiation level between different instruments and to take this into consideration when weighing the factors determining the choice of a new instrument at the time of its purchase.

They get upset to learn that the video game console requires them to use their hands to play it, and one exclaims “That’s a baby’s game!” I’m thinking “Whoa, I never want to be that dependent on technology that I don’t want to use my hands. I’ve heard many people say “my cell phone is my right arm, or I can’t live without my cell phone. How many of you recall the movie “Johnny Mnemonic(1995)” It was about the effect technology was having on the human body. Nerve Attenuation Syndrome (NAS)

INTEGRITY: Many manufactures claim near 100% EMF protection, referring to the radiation blocking material, NOT the protection you receive on a call. If you covered your whole phone with EMF blocking material, then you'd have no signal. Our EMF blocking material is used on the front cover only, providing you real EMF protection with no sacrifice in reception.


“This means we’re on the beginning curve of an epidemic, with epidemic defined as a change in the occurrence of a disease that is so dramatic in its increase that it portends serious public health consequences,” says Dr. Carlo. “This is what’s not being told to the public. One of the things that I suggest to people who use a cell phone is to use an air tube headset. If you use a wired headset, the current moving through the wire of the headset attracts ambient informational carrying radio waves and thereby increases your exposure.”
Jump up ^ Repacholi MH, Lerchl A, Röösli M, Sienkiewicz Z, Auvinen A, Breckenkamp J, d'Inzeo G, Elliott P, Frei P, Heinrich S, Lagroye I, Lahkola A, McCormick DL, Thomas S, Vecchia P (2012). "Systematic review of wireless phone use and brain cancer and other head tumors". Bioelectromagnetics (Systematic review). 33 (3): 187–206. doi:10.1002/bem.20716. PMID 22021071.

Pong’s claims for its case have stood up to the scrutiny of Wired magazine and the Better Business Bureau (Advertising Self-Regulation Council 2012; Ganapati 2009). In tests conducted by Cetecom, a cell phone radiation certification lab, and observed by a reporter from Wired magazine, an iPhone 3G tested without a case had a maximum SAR of 1.18 W/kg when held at the ear. The same phone tested with a Pong case had a maximum SAR of 0.42 W/kg (Ganapati 2009).  
Independently tested DefenderShield® technology uses a patent-pending sophisticated layering of separate non-toxic, human safe exotic materials processed for maximum radiation blocking efficiency. Each material has unique and targeted radiation shielding characteristics designed to work in unison to up to eliminate all radiation emissions from 0 to 10 GHz.
The cell phone industry constantly guards its financial interests, but unfortunately, an unwitting public can be harmed in the process, says Dr. Carlo. “Industry-funded studies in many cases now produce industry-desired outcomes. By tampering with the integrity of scientists, scientific systems and public information steps over the lines of propriety that are appropriate for protecting business interests—especially when the casualty of the interference is public health and safety.”
There is some concern that my iphone was working even when turned off, as it would somehow use the battery over the coarse of a few months of being turned off. So long as it isn’t government mandated that we not interfere with their ability to find our phone when they want, I want to make sure they can’t. Yes they can argue only a terrorist would want that. But I’m no terrorist and I want that because like millions of Americans, I dislike the idea of Big Brother constantly keeping digital tabs on me.

Although recall bias is minimized in studies such as COSMOS that link participants to their cell phone records, such studies face other problems. For example, it is impossible to know who is using the listed cell phone or whether that individual also places calls using other cell phones. To a lesser extent, it is not clear whether multiple users of a single phone, for example family members who may share a device, will be represented on a single phone company account. Additionally, for many long-term cohort studies, participation tends to decline over time.
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