With the use of cell phones and other wireless devices on the rise, concerns have been raised about possible associated health risks, especially cancer (if you’ve been keeping up with our articles about wireless health risks, skip to the next paragraph). Over the years, numerous studies have been conducted to assess relative risk of thermal health effects like cancer and non-thermal health effects like immune system response; however, diverse results have prevented across-the-board conclusions about whether standards governing wireless emissions should be revised in order to protect public health. Many experts advocate the practice of precautionary cell phone use, and almost all agree, “more research is necessary.”
Recently, though, two studies have been published that give researchers more tangible information to sink their teeth into about the immediate physiological effects of cell phone use, specifically how it affects heart and brain function. In 2010, Havas, et al. demonstrated that talking on a cordless phone(which operates at the same radio frequency, or "RF," as WiFi) can directly impact heart function; forty percent of Havas' study participants experienced changes in heart rhythm, heart rate, or heart rate variability after exposure to cordless phone emissions during three-minute intervals. This year, Nora Volkow, M.D. and her research grouppublished data showing that 50 minutes of cell phone use causes the region of the brain closest to the phone antenna to utilize more glucose for fuel. Although the clinical significance of increased glucose metabolism remains to be determined, this finding proves that cell phone use impacts how our brains function.
The Volkow Study: Cell Phone Use Linked to Changes in Brain Function
Throughout 2009, Volkow’s group conducted a randomized crossover studywith 47 healthy participants, testing the effects of 50 minutes of cell phone use on the subjects' brain activity. The researchers conducted two separate experiments on each study participant, both of which involved placing cell phones on each of the participant’s ears, then measuring how his or her brain metabolized glucose using positron emission tomography (PET scans) with injections of (18F)fluorodeoxyglucose. The study participants were “blinded” as to whether both of the cell phones were turned off, or the one on the right was turned on and receiving a prerecorded text (with the sound muted). Overall, Volkow’s group found that exposure to cell phone radiation caused brain cells closest to the antenna to metabolize more sugar than they would when not exposed to the RF radiation.
Do the Results Indicate that Cell Phone Use is Harmful?
Not surprisingly, Volkow’s group concluded that “more research is necessary” to determine if increased glucose metabolism in response to RF exposure actually increases risk of health problems. The basic results of this study are monumental, though. Because altered cell physiology must be shown in order to prove the possibility of related health effects, demonstrating a link between altered brain activity in the human model and cell phone use proves that cell phone radiation may cause non-thermal health effects in the human brain.
Interestingly enough, Volkow’s group determined that increased glucose metabolism in brain cells was a secondary effect. In other words, exposure to RF emissions caused some other primary effect(s) which led to brain cells using more sugar than they normally would. The researchers hypothesized that enhanced excitability of brain tissue, neurotransmitter release, increased cell membrane permeability, calcium efflux, and disruption of the blood-brain barrier could all be primary effects.
In an editorial related to the study (and published in the same issue of JAMA) Professor Henri Lai, expert on non-thermal effects associated with non-ionizing radiation, and Professor Lennart Hardell, expert on environmental toxins and cancer development, noted several important findings in the 2011 Volkow et al.study. One of which was, that the increased glucose metabolism effect is probably not caused by heating of tissues. Rather, since the brain regions affected were closer to the antenna, rather than the phone itself, the changes were due to RF energy emitted from the antenna when connecting to a base station signal, not the heating of the phone itself (skin temperature can increase up to 2 degrees Celsius after 10 minutes of contact with an operative phone). Hardell and Lai also suggested that more research be done to address whether regular use of cell phones and other wireless technologies could cause chronicincrease in brain glucose metabolism, and, if so, how such increase would impact health.
Increased Brain Glucose Metabolism and EHS?
Numerous individuals, deemed as having “electrohypersensitivity” (“EHS”) by authorities, have reported symptoms including headaches, cognitive difficulties, dizziness, heart palpitations and arrhythmias when exposed to electromagnetic fields (EMFs). By demonstrating that acute exposure to RF emissions can cause heart beat irregularities in human subjects, the Havas group recently created a tangible nexus between exposure to RF emissions and arrhythmia, which had been a frequently reported, yet "unproved," EHS symptom. If a connection can be made between increased brain glucose metabolism and neurological EHS symptoms, then the Volkow study may prove to be another valuable piece of the puzzle surrounding mechanisms of possible non-thermal health effects associated with RF exposure.
Glucose on the Brain:Food for Thought...
Glucose, a simple sugar, is a primary food source for the body, especially for the brain. Our digestive systems break down carbohydrates into glucose molecules which are then carried through the blood to be escorted into cells by insulin. The amount of glucose in the blood affects the amount of insulin released by the pancreas, and ultimately affects overall hormonal balance in the body. Could a chronic increase in the metabolism of glucose in the brain eventually place a person at greater risk of insulin related health issues?
When we are “stressed,” our sympathetic nervous systems are activated and setting off physiological “fight or flight” responses, more glucose becomes available in the blood as a quick source of energy for the body. Increased glucose metabolism in the brain may indicate that cells respond to RF emissions as “stressors,” and that cellular stress response is the primary mechanism behind non-thermal effects.
Cancer cells thrive on sugar. They rely on anaerobic (i.e. without oxygen) respiration to break down glucose molecules into fuel. Could increased glucose metabolism in brain cells be linked to the development of brain cancer?
As the Volkow group concluded, more research is necessary to establish whether actual health risks are associated with increased brain glucose metabolism due to cell phone use. Given what we've just learned from this study, practicing precautionary cell phone (as well as cordless phone and WiFi) use seems the smartest option until we learn more about long-term effects. Use text messaging instead of calling, whenever possible, utilize the speakerphone function when making or receiving calls, and limit children's use to emergencies.
References and Resources:
Volkow ND, Tomasi D, et al. Effects of Cell Phone Radiofrequency Signal Exposure on Brain Glucose Metabolism. JAMA. 2011;305(8):808-813. [Abstract]
Lai H, Hardell L. Cell Phone Radiofrequency Radiation Exposure and Brain Glucose Metabolism. JAMA. 2011;305(8):828-829. [Extract]
EMF Studies showing links between RF emissions and possible non-thermal health effects