Regular Cell Phone Use Linked to Higher Heart Disease Risk

Using a cell phone for at least one call per week is linked to a higher risk for cardiovascular disease (CVD), especially among smokers and patients with diabetes, according to a new UK Biobank analysis.

“We found that a poor sleep pattern, psychological distress, and neuroticism significantly mediated the positive association between weekly mobile phone usage time and the risk for incident CVD, with a mediating proportion of 5.11%, 11.50%, and 2.25%, respectively,” principal investigator Xianhui Qin, MD, professor of nephrology at Southern Medical University, Guangzhou, China, told Medscape Medical News.

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

In addition, chronic exposure to radiofrequency electromagnetic fields (RF-EMF) emitted from cell phones could lead to oxidative stress and an inflammatory response. Combined with smoking and diabetes, this exposure “may have a synergistic effect in increasing CVD risk,” Qin suggested.

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

Risk Underestimated?

The researchers aimed to examine the association of regular cell phone use with incident CVD 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) without a history of CVD from the UK Biobank. A total of 378,161 participants were regular cell phone users.

Regular cell phone use was defined as at least one call per week. Weekly use was self-reported as the average time of calls per week during the previous 3 months.

The primary outcome was incident CVD. Secondary outcomes were each component of CVD (ie, coronary heart disease, stroke, atrial fibrillation, and heart failure) and increased carotid intima media thickness (CIMT).

Compared with nonregular cell phone users, regular users were younger, had higher proportions of current smokers and urban residents, and had lower proportions of history of hypertension and diabetes. They also had higher income, Townsend deprivation index, and body mass index and lower education levels.

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

Among regular cell phone users, the duration of cell phone use and hands-free device/speakerphone use during calls was not significantly associated with incident CVD. Yet a significant and positive dose-response relationship was seen between weekly cell phone usage time and the risk for CVD. The positive association was stronger in current vs noncurrent smokers and people with vs without diabetes.

To different extents, sleep patterns (5.11%), psychologic distress (11.5%), and neuroticism (2.25%) mediated the relationship between weekly cell phone usage time and the risk for incident CVD.

“Our study suggests that despite the advantages of mobile phone use, we should also pay attention to the potential harm of mobile phone use to 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.”

Meanwhile, he added, “We encourage measures to reduce time spent on mobile phones to promote the primary prevention of CVD. On the other hand, improving sleep and mental health status may help reduce the higher risk of CVD associated with mobile phone use.”

There are several limitations to the study in addition to its observational nature, which cannot show cause and effect. The questionnaires on cell phone use were restricted to phone calls; other use patterns of cell phones (eg, messaging, watching videos, and browsing the web) were not considered. Although the researchers adjusted for many potential confounders, unmeasured confounding bias (eg, the type of cell phone used and other sources of RF-EMF) cannot be eliminated.

Weak Link?

Commenting on the study for Medscape Medical News, Nicholas Grubic, MSc, a PhD student in epidemiology at the University of Toronto, Toronto, Ontario, Canada, and co-author of a related editorial, said, “I found it interesting that there was a connection observed between mobile phone use and CVD. However, it is crucial to understand that this link appeared to be much weaker compared with 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.”

Nevertheless, clinicians should encourage patients to practice healthy habits around their screen time, he advised. “This could include limiting mobile phone use before bedtime and taking regular breaks to engage in activities that promote heart health, such as exercising or spending time outdoors.

“For the time being, we probably won’t see mobile phone use included in standard assessments for cardiovascular risk or as a focal point of cardiovascular health promotion initiatives,” he added. Instead, clinicians should “focus on established risk factors that have a stronger impact on patients’ cardiovascular health.”

Nieca Goldberg, MD, a clinical associate professor of medicine at NYU Grossman School of Medicine in New York City and American Heart Association volunteer expert, had a similar message. “You don’t have to go back to using a land line,” she said. “Instead, patients should be more mindful of how much phone use is taking away from their physical activity, keeping them from sleeping, and causing them stress.” Clinicians should also remember to counsel smokers on smoking cessation.

“It would be important for future studies to look at time spent on the phone and the type of activities patients are doing on their phones, such as social media, calls, texts, movies, or streaming TV shows,” she said. “It would be important to see how phone use is leading to a sedentary lifestyle” and what that means for a larger, more diverse population.

The study was supported by the National Key R&D Program, the National Natural Science Foundation of China, and the Outstanding Youth Development Scheme of Nanfang Hospital, Southern Medical University. Qin, Grubic, and Goldberg reported having 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.