Do mobile phones pose a potential risk to autonomic modulation of the heart?

Effects of man-made electromagnetic fields on heart rate variability parameters of general public: a systematic review and meta-analysis of experimental studies

OBJECTIVES

The effects of man-made electromagnetic fields (EMFs) on the cardiovascular system have been investigated in many studies. In this regard, the cardiac autonomic nervous system (ANS) activity due to EMFs exposure, assessed by heart rate variability (HRV), was targeted in some studies. The studies investigating the relationship between EMFs and HRV have yielded conflicting results. We performed a systematic review and meta-analysis to assess the data's consistency and identify the association between EMFs and HRV measures.

CONTENT

Published literature from four electronic databases, including Web of Science, PubMed, Scopus, Embase, and Cochrane, were retrieved and screened. Initially, 1601 articles were retrieved. After the screening, 15 original studies were eligible to be included in the meta-analysis. The studies evaluated the association between EMFs and SDNN (standard deviation of NN intervals), SDANN (Standard deviation of the average NN intervals for each 5 min segment of a 24 h HRV recording), and PNN50 (percentage of successive RR intervals that differ by more than 50 ms).

SUMMARY

There was a decrease in SDNN (ES=-0.227 [-0.389, -0.065], p=0.006), SDANN (ES=-0.526 [-1.001, -0.05], p=0.03) and PNN50 (ES=-0.287 [-0.549, -0.024]). However, there was no significant difference in LF (ES=0.061 (-0.267, 0.39), p=0.714) and HF (ES=-0.134 (0.581, 0.312), p=0.556). In addition, a significant difference was not observed in LF/HF (ES=0.079 (-0.191, 0.348), p=0.566).

OUTLOOK

Our meta-analysis suggests that exposure to the environmental artificial EMFs could significantly correlate with SDNN, SDANN, and PNN50 indices. Therefore, lifestyle modification is essential in using the devices that emit EMs, such as cell phones, to decrease some signs and symptoms due to EMFs' effect on HRV.

Electromagnetic fields - do they pose a cardiovascular risk?

Mobile wireless communication technologies have now become an everyday part of our lives, 24 hours a day, 7 days a week. Monitoring the autonomous system under exposition to electromagnetic fields may play an important role in broading of our still limited knowledge on their effect on human body. Thus, we studied the interaction of the high frequency electromagnetic field (HF EMF) with living body and its effect on the autonomic control of heart rate using Heart Rate Variability (HRV) linear and nonlinear analyses in healthy volunteers. A group of young healthy probands (n=30, age mean: 24.2 ± 3.5 years) without any symptoms of disease was exposed to EMF with f=2400 MHz (Wi Fi), and f=2600 MHz (4G) for 5 minutes applied on the chest area. The short-term heart rate variability (HRV) metrics were used as an indicator of complex cardiac autonomic control. The evaluated HRV parameters: RR interval (ms), high frequency spectral power (HF-HRV in [ln(ms2)]) as an index of cardiovagal control, and a symbolic dynamic index of 0V %, indicating cardiac sympathetic activity. The cardiac-linked parasympathetic index HF-HRV was significantly reduced (p =0.036) and sympathetically mediated HRV index 0V % was significantly higher (p=0.002) during EMF exposure at 2400 MHz (Wi-Fi), compared to simulated 4G frequency 2600 MHz. No significant differences were found in the RR intervals. Our results revealed a shift in cardiac autonomic regulation towards sympathetic overactivity and parasympathetic underactivity indexed by HRV parameters during EMF exposure in young healthy persons. It seems that HF EMF exposure results in abnormal complex cardiac autonomic regulatory integrity which may be associated with higher risk of later cardiovascular complications already in healthy probands.

Association of Autonomic Balance With Phone Call Duration in Healthy Individuals

Background This study aimed to estimate the association of autonomic balance with the duration of phone calls in healthy individuals. Methodology A total of 30 subjects aged between 18 and 30 years without any established systemic disease and using mobile phones for more than five years with minimum daily usage of 30 minutes were included in this analytical study. Heart rate variability (HRV) was recorded using a three-channel physiograph (AD Instruments South Asia (India) Pvt. Ltd., New Delhi, India) with the software LabChart PROV8.1.8 with HRV Module version 2.0.3 for 10 minutes. Time domain parameters were recorded in terms of the standard deviation of normal to normal interval (SDNN), root mean square of successive differences between normal heartbeats (RMSSD), R-R intervals greater than 50 ms (pRR50), and mean heart rate (MHR), and frequency domain parameters were total power, low-frequency power (LF), high-frequency power (HF), and the ratio of low-frequency to high-frequency power (LF/HF). HRV was recorded three times in each subject that included baseline HRV, HRV during the use of a mobile phone, and HRV after the use of a mobile phone. Results A total of 30 subjects (14 males and 16 females) participated in this study. The mean age of participants was 31.93 ± 8.59 years (32.07 ± 9.87 years for males, and 31.81 ± 7.64 years for females). There were no findings of significant arrhythmia in any of the participants. There was a significant difference in pRR50 on comparing all three phases (p = 0.036). However, there was no significant variation in other parameters such as very low frequency (VLF, ms²), VLF (%), LF (ms²), LF (%), HF (ms²), HF (%), LF/HF, SDNN (ms), RMSSD (ms), Poincare plot standard deviation perpendicular to the line of identity (ms), Poincare plot standard deviation along the line of identity (ms), systolic blood pressure (mmHg), and diabolic blood pressure (mmHg) during, before, and after exposure to mobile phone calls. There was no significant difference in the value of all parameters between males and females (p < 0.05). Conclusions Mobile phone calls may influence HRV and autonomic balance. This change may be affected by the electromagnetic field and by speaking as well.

Establishment of injury models in studies of biological effects induced by microwave radiation

Microwave radiation has been widely used in various fields, such as communication, industry, medical treatment, and military applications. Microwave radiation may cause injuries to both the structures and functions of various organs, such as the brain, heart, reproductive organs, and endocrine organs, which endanger human health. Therefore, it is both theoretically and clinically important to conduct studies on the biological effects induced by microwave radiation. The successful establishment of injury models is of great importance to the reliability and reproducibility of these studies. In this article, we review the microwave exposure conditions, subjects used to establish injury models, the methods used for the assessment of the injuries, and the indicators implemented to evaluate the success of injury model establishment in studies on biological effects induced by microwave radiation.

Evaluation of heart rate variability, blood pressure and lipid profile alterations from dual transceiver mobile phone radiation exposure

OBJECTIVES

Electromagnetic fields have been reported to alter electrical activities in the brain and heart. However, there is paucity of information on the potential functional alterations that magnetic fields from mobile phone could cause to the heart. This study investigated heart rate variability (HRV), blood pressure (BP) and lipid profile in Wistar rats exposed to electromagnetic field radiation from a dual transceiver mobile phone (DTrMP).

METHODS

Twenty-one male albino Wistar rats (140-180 g) were randomly assigned to two major groups positioned 5 m apart as follows: control: no phone (n=7) and treatment group (n=14) continuously exposed to electromagnetic field from Tecno T312 DTrMP 900/1800 MHz set in silence mode. Experimental treatment consisted in 10 min calls/day, directed to this device for a period of six weeks. Seven animals from the treatment group were allowed to recover for a period of two weeks after exposure. HRV, systolic, diastolic and mean arterial BP were noninvasively investigated, while serum lipid profile and heart tissue nitric oxide (NO) activities were determined using standard procedures.

RESULTS

There was significant (p<0.05) increase in systolic, diastolic, mean arterial BP and a decrease in HRV. Serum high density lipoproteins decreased, while total cholesterol, atherogenic indices, and heart NO levels increased significantly in the radiation exposed animals. The alterations observed in exposed animals remained unchanged even after the recovery period.

CONCLUSIONS

These results suggest that exposure to electromagnetic radiation from dual transceiver mobile phones could be a risk factor to increase in blood pressure.

Cellular Phone User's Age or the Duration of Calls Moderate Autonomic Nervous System? A Meta-Analysis

BACKGROUND

The European Health Risk Assessment Network on Electromagnetic Fields Exposure (EFHRAN) reported in 2012: "Children and adolescents represent the first generation of Europeans to be exposed to diffuse EMF since their conception and birth, thus, they are expected to be more sensitive to these fields." On the other hand, the body's physiologic processes are regulated by the autonomic nervous system (ANS) in a way that warrants further elucidation.

OBJECTIVE

Age and duration of exposure are investigated for modifying the variance of the reported effects of mobile/cellular phone call (CPC) on ANS indexed, herein, by the heart rate variability (HRV).

METHOD

Five studies targeted to 124 healthy subjects (aged 15.3-28.4 years (24.3 ± 5.2), who have been recorded in supine position before and/or sham versus real exposure (to a CPC lasting 5-32 minutes), are included in this meta-analysis. Age and duration of a CPC are evaluated as predictors in two separate meta-regressions.

RESULTS

The meta-analysis identified a heterogeneity I² = 63.2% for all outcomes and I² = 65.2% for sympathovagal balance. Thus, we performed meta-regressions: for the sympathovagal balance rather than the combined parameters effect, the goodness of fit model presents significance only for age - the residual sum of squares compared to chi-square distribution (Q_R) is 4.24 for age (p = 0.12) - while, for minutes of exposure, Q_R = 8.2805 (p = 0.016).

CONCLUSIONS

The sympathovagal balance - indispensible for health/homeostasis maintenance - is strongly predicted by age. Minutes of exposure did not affect overall HRV or sympathovagal balance. The results endorse/validate the EFHRAN 2012 suggestion for future research targeting to youngsters.

Exposure to cell phones reduces heart rate variability in both normal-weight and obese normotensive medical students

BACKGROUND

We investigated and compared the effect of the radiofrequency electromagnetic field (RF-EM) emitted by a cell phone on the electrocardiogram and heart rate variability (HRV) of normotensive normal-weight and obese medical students.

METHOD

Twenty medical student volunteers, normal weight (age = 23 ± 2, BMI = 23.05 ± 1.72) or obese (age = 24 ± 2, BMI = 32.39 ± 4.78), were exposed to a cell phone (1) close to the heart in silent mode, no ringing or vibrating; (2) close to the heart in ring and vibration mode; (3) next to the ear (brain) while listening; and (4) next to the ear while listening and speaking.

RESULTS

The average basal HR of obese students significantly increased, while the PR interval; time domains, including standard deviation (SD) of all normal R-R intervals (SDNN), mean of the SD of all normal R-R intervals (SDNNi), SD of the average of normal R-R intervals (SDANN), and percentage of R-R intervals at least 50 ms different from the previous interval (pNN50); and high-power frequency (HF) decreased. The LF/HF ratio also significantly increased. The SDNN, SDNNi, SDANN, pNN50, and HF levels significantly decreased and the LF/HF significantly increased in normal-weight and obese individuals only when the phone was near the apex of the heart in ring and vibration mode. All changes were more profound in obese students.

CONCLUSION

Keeping the phone in a chest pocket reduced the HRV of normal-weight and obese medical students and exaggerated the effect of obesity on sympathetic activation.

The effects of the duration of mobile phone use on heart rate variability parameters in healthy subjects

Objective:

This study aimed to estimate the influence of the duration of mobile phone use on heart rate variability (HRV) in healthy individuals.

Methods:

One hundred forty-eight individuals without any established systemic disease and who had undergone 24-h ambulatory ECG monitoring were included in the case-control study. All the individuals had been using mobile phones for more than 10 years. Three-channel 24-h Holter monitoring was performed to derive the mean heart rate, standard deviation of normal NN intervals (SDNN), standard deviation of 5-min (m) mean NN intervals (SDANN), the proportion of NN50 divided by the total number of NNs (pNN50), the root mean square differences of successive NN intervals (RMSSD), high (HF)-, low (LF)-, very low (VLF)-frequency power, total power components, and the LF/HF ratio. Individuals were divided into four groups according to their duration of mobile phone use [no mobile phone use (Control group), <30 min/day (Group 1), 30–60 min/day (Group 2), and >60 min/day (Group 3)].

Results:

All the groups had similar features with regard to demographic and clinical characteristics. No significant arrhythmias were observed in any of the groups. The LF/HF ratio was higher, whereas the SDNN, SDANN, RMSSD, and pNN50 values were lower in the study groups than in the control group (p<0.05). No significant differences were identified among groups with respect to heart rate, VLF, and total power values (p>0.05).

Conclusion:

In this study, it was shown that the duration of mobile phone use may affect the autonomic balance in healthy subjects. The electromagnetic field created by mobile phone use may induce HRV changes in the long term.

Nonlinear heart rate variability measures under electromagnetic fields produced by GSM cellular phones

This study was designed to assess the nonlinear dynamics of heart rate variability (HRV) during exposure to low-intensity EMFs. Twenty-six healthy young volunteers were subjected to a rest-to-stand protocol to evaluate autonomic nervous system in quiet condition (rest, vagal prevalence) and after a sympathetic activation (stand). The procedure was conducted twice in a double-blind design: once with a genuine EMFs exposure (GSM cellular phone at 900 MHz, 2 W) and once with a sham exposure (at least 24 h apart). During each session, three-lead electrocardiograms were recorded and RR series extracted off-line. The RR series were analyzed by nonlinear deterministic techniques in every phase of the protocol and during the different exposures. The analysis of the data shows there was no statistically significant effect due to GSM exposure on the nonlinear dynamics of HRV.

An update on mobile phones interference with medical devices

Mobile phones' electromagnetic interference with medical devices is an important issue for the medical safety of patients who are using life-supporting medical devices. This review mainly focuses on mobile phones' interference with implanted medical devices and with medical equipment located in critical areas of hospitals. A close look at the findings reveals that mobile phones may adversely affect the functioning of medical devices, and the specific effect and the degree of interference depend on the applied technology and the separation distance. According to the studies' findings and the authors' recommendations, besides mitigating interference, using mobile phones at a reasonable distance from medical devices and developing technology standards can lead to their effective use in hospital communication systems.

Electromagnetic energy radiated from mobile phone alters electrocardiographic records of patients with ischemic heart disease

Background:

Electromagnetic energy radiated from mobile phones did not show significant effect on the blood pressure, heart rate, and electrocardiographic (ECG) parameters in animals and humans.

Aim:

This study aimed to investigate the effect of radiofrequency of mobile phone on the electrocardiographic parameters in patients with history of ischemic heart disease, taking into consideration the gender factor.

Subjects and Methods:

A total number of 356 participants (129 males and 227 females) were admitted in this study. They were grouped into: subjects without cardiac diseases (Group I), patients with ischemic heart disease (Group II), and patients with history of cardiac diseases not related to myocardial ischemia (Group III). Electrocardiogram was obtained from each patient when the mobile phone was placed at the belt level and over precordium in turn-off mode (baseline) and turn-on mode for 40 sec ringing. The records of ECG were electronically analyzed.

Results:

Prolongation of QTc interval was significantly observed in male gender of Groups I and III (P < 0.001). Male patients of Group II showed significant QTc interval prolongation (P = 0.01) and changes in the voltage criteria (P = 0.001). These changes were not observed in female patients with ischemic heart disease. The position of mobile at the belt level or over the precordium showed effects on the heart.

Conclusions:

The radiofrequency of cell phone prolongs the QT interval in human beings and it interferes with voltage criteria of ECG records in male patients with myocardial ischemia.