Headaches, a common problem for many people (10-20% of adolescents), are a symptom that can be triggered by mobile phone use. Mobile phone use may be responsible for certain types of headaches, dizziness, neck and shoulder pain, stress and organ strain, and sleep disturbances. There is some evidence suggesting a causal relationship between headaches and mobile phone use. However, there are conflicting reports in the literature. Some studies have identified a statistically significant association, while others with controlled exposure duration have reported non-significant associations. In this context, a systematic review could help clarify the inconsistencies regarding the effects of mobile phone electromagnetic fields (EMFs) on headaches.
A previous systematic review (Wong et al., 2017) focused on the relationship between mobile phone call duration and headaches and found a causal link between call duration and headaches. The current systematic review included more studies and considered the impact of age as another factor in addition to the duration of EMF exposure from mobile phones (primarily call duration).
The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed for this systematic review. The Web of Science, PubMed, and Scopus databases were searched for studies. The search was limited to the period from 1990 to February 2021, as mobile phone use was virtually non-existent before 1990. The PICO model (Population, Intervention, Comparison, and Outcome) was used to identify relevant studies. Only studies involving digital (as opposed to analog) mobile phones were considered. All subtypes of headaches were included in the current study. There were no age restrictions for participants and no limitations on the duration of EMF exposure, as exposure duration and age were also considered as potential moderator variables for possible effects.
Study quality was assessed using the National Institutes of Health (NIH) quality assessment tool for observational cohort and cross-sectional studies. The adjusted odds ratio (OR) was extracted or calculated based on the reported results (per study).
Thirty-three eligible studies were selected for further analysis. Some of these studies found a statistically significant effect of EMF exposure from mobile phones or base stations on headaches (n = 25). The total number of participants in the included studies was 109,385 (approximately 73.24% female). Some studies reported more than one effect size for different exposure conditions. In this context, a total of 58 effect sizes were identified for the effects of EMF emitted by mobile phones or base stations on different types of headaches. Thirty studies provided sufficient information to calculate the OR and were included in the meta-analysis.
Of the 33 included studies, 21% were of low quality (quality score < 7), 70% were of medium quality (7 ≤ quality score < 10), and 9% were of high quality (quality score ≥ 10). When all studies with different age ranges, exposure durations, and EMF-generating devices (i.e., mobile phones and base stations) were considered, the pooled effect was OR = 1.30 (95% CI 1.21-1.39), indicating a significant effect of EMF on headaches. However, the heterogeneity between the studies was relatively high (I² = 72.2%, p < 0.01).
To investigate the source of heterogeneity, age range and exposure duration were examined as potential influencing factors. For the subgroup analysis using participant age as a moderating variable, studies were divided into three categories: studies with participants aged ≤ 18 years, studies with participants older than 18 years, and studies without age-specific results.
For the subgroup analysis considering exposure duration as a moderator variable, studies were divided into two groups: EMF exposure from mobile phones for more than 100 minutes per week, EMF exposure for 100 minutes per week or less.
Based on the effect sizes and analysis of variance for these groups, no effect was found for age or the interaction between exposure duration and age. However, a significant effect was observed for exposure duration. When the age of the participants was limited to ≤ 18 years, the pooled effect size was OR = 1.29 (95% CI 1.20-1.37), with moderate heterogeneity between studies (I² = 45.2%, p = 0.004). For adults (> 18 years), a larger effect was observed (OR = 1.33, 95% CI 1.14-1.53), with statistically non-significant heterogeneity (I² = 2.30%, p = 0.408). For individuals exposed to mobile phone EMF: ≤ 100 minutes/week: OR = 1.23 (95% CI 1.12-1.34), moderate heterogeneity (I² = 63.7%, p < 0.001);
> 100 minutes/week: OR = 1.41 (95% CI 1.22-1.61), significant heterogeneity (I² = 77.4%, p = 0.00).
For individuals exposed to EMF from mobile phone base stations, the pooled effect on headaches was OR = 1.14 (95% CI 0.75-1.52), indicating a smaller, non-significant effect compared to actual mobile phone use.
The pooled effect of mobile phone use on headaches was OR = 1.30 (95% CI 1.21-1.39), indicating a significant effect of mobile phone use on headache prevalence. This is consistent with recent findings from a Mendelian randomization study (He, 2024, also reviewed in this ElektrosmogReport), which reported an OR of 1.40 (95% CI 1.03-1.90) for migraine prevalence.
For both age groups (≤ 18 and > 18 years), the pooled effect of EMF exposure on headache risk was lower for shorter EMF exposure durations. The headache risk for the higher exposure group (OR 1.41 for > 100 min/week) was about twice that of the lower exposure group (OR 1.21 for ≤ 100 min/week). An increased risk of headaches with longer exposure duration was observed in both younger and older participants.
These findings are consistent with a previous meta-analysis of seven studies (Wong et al. 2017), which also reported an increased risk of headaches with longer exposure duration. The results of the current study further suggest that mobile phone users have a higher risk of headaches compared to individuals living near mobile phone base stations.
Editor's note: Since obtaining accurate exposure data near base stations is even more challenging than exposure from mobile phones, this issue should be re-evaluated in future studies with improved dosimetry. (AT)