Radiofrequency radiation from mobile phones and the risk of breast cancer: A multicenter case-control study with an additional suspected comparison group.

Several large cohort and case-control studies have examined the relationship between mobile phone use and brain tumors. However, the results are inconclusive, and there is little evidence of an association with other malignant tumors, such as breast cancer. Current findings from large cohort studies do not support a clear link between mobile phone use and an increased overall cancer risk. To address this knowledge gap, the authors conducted a multicenter case-control study that included an additional comparison group of individuals receiving radiation therapy for suspected cancer at medical centers in Iran.

A total of 226 women were included in the final analysis: 77 had confirmed breast cancer, 52 had suspected breast cancer, and 97 were control subjects. Although conventional case-control studies usually include more control subjects, the limited number of suitable volunteers resulted in an imbalanced ratio. Logistic regression models were used to account for this imbalance without compromising analytical validity. Trained interviewers administered a structured questionnaire that included data on demographics, reproductive history, lifestyle, and the environment. This questionnaire also included questions about the duration of mobile phone use, screen time, and phone placement. The associations were analyzed using multinomial logistic regression with sequential adjustments for demographic, reproductive, environmental, and lifestyle variables. Two multivariable models were created: Model 1 was adjusted for age, weight, education, and reproductive factors (e.g. age at menarche). Model 2 builds on Model 1 by including environmental and lifestyle variables such as exposure to pollutants, sleep habits, mobile phone use, and screen time.

Several lifestyle factors differed significantly between the groups. These factors included the number of pregnancies (p < 0.001), consumption of fruits and vegetables (p < 0.001), income level (p = 0.017), use of hormone therapy (p = 0.015), history of surgery or biopsies (p = 0.007), exposure to pollutants (p = 0.036), time spent outdoors (p < 0.001), duration of mobile phone calls (p = 0.004), screen time (p = 0.003), difficulty falling asleep (p = 0.003), and early morning awakening (p = 0.001). However, there were no statistically significant differences between the groups in terms of other variables, such as drug use, menopausal status, fat intake, sugar consumption, processed food consumption, radiation therapy, alcohol consumption, and physical activity.

In the fully adjusted model (Model 2), some variables were associated with a higher risk of confirmed and/or suspected breast cancer.

• Educational level was significantly associated with case status (high school: OR = 5.11 [1.5–17.9], p = 0.011).

• Age at menarche was a significant predictor of case status (OR = 1.39 [1.0–1.9], p = 0.040).

• Exposure to pollutants was strongly associated with case status (OR = 7.29 [1.9–27.8], p = 0.004).

• The duration of mobile phone calls was significant. More than 60 minutes of phone use was associated with both confirmed (OR = 3.49, 95% CI: 1.0–11.9, p = 0.046) and suspected (OR = 10.84 [2.3–51.4], p = 0.003) cases.

• Longer screen time (> 4 hours/day) was also associated with increased odds.

This study sheds new light on how lifestyle and environmental factors – such as mobile phone use, screen time, and light-at-night exposure – may impact breast cancer development. The most consistent and robust finding was the significant association between longer daily mobile phone use and an increased risk of breast cancer. Compared to women who reported using their phones for less than 10 minutes per day, women who used their phones for more than 60 minutes per day were 3.5 times more likely to be diagnosed with confirmed breast cancer and more than 10 times more likely to be classified as suspected cases. This dose-dependent relationship strengthens the biological plausibility of a link between long-term RF-EMF exposure and breast cancer development.

In this multinomial analysis, longer mobile phone use was associated with an increased risk of both suspected and confirmed breast cancer cases. However, this association does not establish causality because exposure was not measured independently and potential confounding factors cannot be ruled out. Therefore, these results should be interpreted with caution. Larger prospective studies with objective exposure measurements are needed to clarify whether this association reflects causality or merely correlation. (AT)