Regular cell phone use linked to increased risk of heart disease

Using a mobile phone for at least one call per week is linked to a higher risk of cardiovascular disease (CVD), particularly in smokers and diabetic patients, according to a new analysis from UK Biobank.

“We found that poor sleep, psychological distress, and neuroticism significantly moderated the positive association between weekly mobile phone usage time and incident cardiovascular disease risk, with a mediation proportion of 5.11%, 11.50%, and 2.25%, respectively,” said lead researcher Xianhui Qin, MD, professor of nephrology at Southern Medical University, Guangzhou, China. Medscape Medical News.

Poor sleep habits and poor mental health could disrupt circadian rhythms and endocrine and metabolic functions, as well as increase inflammation, he explained.

Additionally, chronic exposure to radiofrequency electromagnetic fields (RF-EMF) emitted by mobile phones could lead to oxidative stress and an inflammatory response. Combined with smoking and diabetes, this exposure “could have a synergistic effect in increasing the risk of cardiovascular disease,” Qin suggested.

The study was published online September 4 in the Canadian Journal of Cardiology.

Underestimated risk?

The researchers wanted to examine the association between regular mobile phone use and incident cardiovascular disease and explore the mediating effects of sleep and mental health using linked hospital and mortality records.

Their analysis included 444,027 participants (mean age, 56 years; 44% men) with no history of cardiovascular disease from the UK Biobank. A total of 378,161 participants were regular mobile phone users.

Regular mobile phone use was defined as at least one call per week. Weekly use was self-reported as the average duration of calls per week over the previous three months.

The primary endpoint was the incidence of cardiovascular disease. Secondary endpoints were each of the components of cardiovascular disease (i.e., coronary heart disease, stroke, atrial fibrillation, and heart failure) and increased carotid intima-media thickness (CIMT).

Compared with occasional mobile phone users, regular users were younger, had a higher proportion of smokers and urban residents, and had less history of hypertension and diabetes. They also had higher income, Townsend deprivation index, and body mass index and lower education level.

During a median follow-up of 12.3 years, 56,181 participants developed incident CVD. Compared with non-regular mobile phone users, regular users had a significantly higher risk of incident CVD (hazard ratio, 1.04) and increased CIMT (odds ratio, 1.11).

Among regular mobile phone users, mobile phone usage time and hands-free/speakerphone use during calls were not significantly associated with the incidence of cardiovascular disease. However, a significant and positive dose-response relationship was observed between weekly mobile phone usage time and cardiovascular disease risk. The positive association was stronger in current smokers than in nonsmokers and in people with diabetes than in people without diabetes.

To varying degrees, sleep habits (5.11%), psychological distress (11.5%), and neuroticism (2.25%) influenced the relationship between weekly mobile phone usage time and risk of cardiovascular events.

“Our study suggests that despite the benefits of mobile phone use, we should also pay attention to the potential adverse effects of mobile phone use on cardiovascular health,” Qin said. “Future studies to assess the risk-benefit balance will help promote mobile phone use patterns that are conducive to cardiovascular health.”

“We encourage measures to reduce the time spent on mobile phones to promote the primary prevention of cardiovascular disease,” he added. “On the other hand, improving sleep and mental health can help reduce the increased risk of cardiovascular disease associated with mobile phone use.”

In addition to its observational nature, the study has several limitations that prevent us from demonstrating a causal relationship. Questionnaires about cell phone use were limited to phone calls; other modes of cell phone use (e.g., messaging, watching videos, and web browsing) were not taken into account. Although the researchers adjusted for many potential confounders, unmeasured confounding biases (e.g., type of cell phone used and other sources of RF-EMF) cannot be eliminated.

Weak link?

Commenting on the study for Medscape Medical NewsNicholas Grubic, a master’s degree in epidemiology and a PhD candidate at the University of Toronto in Ontario, Canada, and co-author of a related editorial, said: “I found it interesting that a link was observed between mobile phone use and cardiovascular disease. However, it is important to understand that this link appears to be much weaker compared to other well-known cardiovascular risk factors, such as smoking, diabetes and high blood pressure. For now, mobile phone use should not be a major concern for most people.”

Still, doctors should encourage patients to adopt healthy habits around their screen time, he advised. “This could include limiting cell phone use before bed and taking regular breaks to engage in activities that promote heart health, such as exercise or spending time outdoors.”

“For now, we are unlikely to see mobile phone use included in standard cardiovascular risk assessments or as a focus of cardiovascular health promotion initiatives,” he added. Instead, clinicians should “focus on established risk factors that have a stronger impact on patients’ cardiovascular health.”

Dr. Nieca Goldberg, an associate clinical professor of medicine at NYU Grossman School of Medicine in New York City and a volunteer expert for the American Heart Association, offered a similar message. “You don’t have to go back to a landline,” she said. “Instead, patients should be more aware of how phone use keeps them from physical activity, keeps them from sleeping and causes them stress.” Clinicians should also consider counseling smokers about quitting.

“It would be important for future studies to look at how much time patients spend on their phones and what types of activities they do on their phones, such as social media, calls, text messages, streaming movies or TV shows,” she said. “It would be important to see how phone use leads to a sedentary lifestyle” and what that means for a broader, more diverse population.

The study was funded by the National Key R&D Program, the National Natural Science Foundation of China, and the Outstanding Youth Development Scheme of Nanfang Hospital of Southern Medical University. Qin, Grubic, and Goldberg have declared no relevant financial relationships.

Marilynn Larkin, MA, is an award-winning medical writer and editor whose work has appeared in numerous publications, including Medscape Medical News and its sister publication MDedge, the Lancet (where she was a contributing editor) and Reuters Health.