Megan Brooks

Using a mobile phone to make or receive calls for just 30 minutes a week is associated with an increased risk of developing hypertension, a large observational study using UK Biobank data suggests.

The study showed adults who spent that at least a half-hour per week on their mobile phone had a 12% increased risk of developing hypertension, whereas those who spent more than 6 hours weekly had a 25% increased risk, compared with a weekly usage time of under 5 minutes.

The investigators caution, however, that the results are purely "hypothesis-generating" and require confirmation, the researchers say.

Experts not involved in the study also urged caution in interpreting the results.

"This study should not be considered a basis to recommend reducing time spent using mobile phones to make calls as a technique to avoid hypertension," Matthew Tomey, MD, cardiologist, Icahn School of Medicine at Mount Sinai in New York City, told theheart.org | Medscape Cardiology. 

"The study is retrospective and, like all retrospective studies, there was a huge risk for unmeasured confounding variables," Mark Estes III, MD, past chair of the American Heart Association scientific publishing committee and the Council on Clinical Cardiology, told theheart.org | Medscape Cardiology.

"There is no need at this point, based on the available evidence, to limit cell phone usage because it might result in higher frequency of hypertension," said Estes, professor of medicine, Division of Cardiology, University of Pittsburgh, Pennsylvania.

The study was published online May 4 in European Heart Journal – Digital Health.

Radiofrequency Energy

Mobile phones emit low levels of radiofrequency energy, which has been associated with increased blood pressure after short-term exposure. However, potential ties between mobile phone use for making and receiving calls and risk of new-onset hypertension remain uncertain, they note.

To investigate, Xianhui Qin, MD, PhD, Southern Medical University, Guangzhou, China, and colleagues evaluated data on 212,046 adults (mean age, 54 years; 62% women) from the UK Biobank without a history of hypertension. 

Information on mobile phone usage to make and receive calls was collected through a self-reported questionnaire at baseline, including years of use, hours per week, and using a hands-free device/speakerphone.

The vast majority (88%) of participants were mobile phone users, defined as using a mobile phone at least once a week.

During a median follow up of 12 years, 13,984 (7%) participants developed new-onset hypertension.

After adjusting for multiple confounding factors, mobile phone users had a 7% higher risk of new-onset hypertension (hazard ratio [HR] 1.07; 95% CI, 1.01 - 1.12; P = .018), compared with non-users.

Among mobile phone users, compared with those with a weekly usage time of less than 5 minutes, significantly higher risks of new-onset hypertension were found in those with a weekly usage time of 30 minutes to more than 6 hours. The results were similar in women and men.

Table. Risk of New-onset Hypertension by Cell Phone Usage

Adults with high genetic risk for hypertension who spent 30+ minutes on their mobile phone had a 33% higher likelihood of new-onset hypertension (HR, 1.33; 95% CI, 1.24 - 1.43) compared with peers with low genetic risk who spent greater than 30 minutes a week on the phone.

Years of mobile phone use and using a hands-free device/speaker phone were not significantly related to the development of hypertension.

Caveats and Cautionary Notes

The investigators caution that the UK Biobank does not include data on the type of mobile phone technology used, and other sources of electromagnetic waves.

Another limitation is that the study population is predominantly White middle-aged adults or White older adults and healthier than the UK general population. A third limitation is that information on mobile phone use was assessed once at baseline and usage might have changed over time.

Tomey noted that the study is not designed to establish a causal linkage and said postulated mechanisms for a biological connection between mobile phone use to make calls and hypertension "remain speculative."

"Among mobile phone users, there were significant differences in almost every measured covariate reported in the baseline characteristics, further reinforcing the need for caution in attributing apparent differences in hypertension to the use of the mobile phones to make calls," Tomey told theheart.org | Medscape Cardiology.

Nonetheless, "we should absolutely be thinking hard about the impact of mobile device usage on our health, not simply about the impact of radiofrequency electromagnetic fields, but more profoundly (and insidiously) about the effects of device usage and media consumption on our attitudes, habits, and psychosocial well-being," Tomey said.

Estes encourages physicians to look at this study as "an opportunity to have a discussion with their patients about hypertension in general and the importance of a low salt diet, regular physical activity, limiting alcohol, maintaining healthy weight, decreasing stress, smoking cessation and, importantly, monitoring your blood pressure yourself and working with your healthcare team."

"Cell phones are irrelevant," when it comes to hypertension, he told theheart.org | Medscape Cardiology.

The study was supported by the National Key Research and Development Program and the National Natural Science Foundation of China. Qin, Tomey, and Estes report no relevant financial relationships.

Eur Heart J Digit Health. Published online May 5, 2023. Full Text

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