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Note: This study found no significant biological effects under its experimental conditions. We include all studies for scientific completeness.

Sleep & Circadian Rhythm

No effects of 900 MHz and 1800 MHz electromagnetic field emitted from cellular phone on nocturnal serum melatonin levels in rats.

No Effects Found

Koyu A, Ozguner F, Cesur G, Gokalp O, Mollaoglu H, Caliskan S, Delibas N. · 2005

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Cell phone radiation showed no effect on melatonin levels in this 4-week rat study, though longer exposures remain unstudied.

Plain English Summary

Summary written for general audiences

Researchers exposed rats to cell phone frequencies (900 MHz and 1800 MHz) for 30 minutes daily over four weeks and measured their nighttime melatonin levels. They found no significant differences in melatonin production between exposed and unexposed rats. This suggests that typical cell phone radiation may not disrupt the body's natural sleep hormone production, at least under these specific exposure conditions.

Why This Matters

This study addresses a critical question about EMF exposure and sleep quality, since melatonin is your body's primary sleep-regulating hormone. The researchers found no impact on melatonin levels from cell phone frequencies, which might seem reassuring at first glance. However, this single study has important limitations. The exposure was relatively brief (30 minutes daily) compared to how many people use their phones throughout the day, and the study only measured one marker of sleep disruption. The science on EMF and sleep remains mixed, with other studies showing effects on sleep quality, brain wave patterns during sleep, and other circadian rhythm markers. What this means for you is that while this particular study didn't find melatonin disruption, it doesn't rule out other ways that EMF exposure might affect your sleep quality or overall health.

Exposure Information

A logarithmic frequency spectrum from 10 Hz to 100 GHz showing where this study's 900 MHz - 1.80 GHz exposure sits relative to common EMF sources.Where This Frequency Sits on the EMF SpectrumELFVLFLF / MFHF / VHFUHFSHFmm10 Hz100 GHzThis study: 900 MHz - 1.80 GHzPower lines50/60 Hz5G mm28 GHzLogarithmic scale

Specific exposure levels were not quantified in this study. The study examined exposure from: 900 MHz and 1800 MHz Duration: 30 min/day, for five days/week for four weeks

Study Details

In this study, the effects of exposure to a 900 MHz and 1800 MHz electromagnetic field (EMF) on serum nocturnal melatonin levels of adult male Sprague-Dawley rats were studied.

Thirty rats were used in three independent groups, 10 of which were exposed to 900 MHz, 10 of which ...

There were no statistically significant differences in serum melatonin concentrations between the 90...

These results indicate that mobile phones, emitting 900 and 1800 MHz EMF, have no effect on nocturnal serum melatonin levels in rats.

Cite This Study
Koyu A, Ozguner F, Cesur G, Gokalp O, Mollaoglu H, Caliskan S, Delibas N. (2005). No effects of 900 MHz and 1800 MHz electromagnetic field emitted from cellular phone on nocturnal serum melatonin levels in rats. Toxicol Ind Health. 21(1-2):27-31, 2005.
Show BibTeX
@article{a_2005_no_effects_of_900_3155,
  author = {Koyu A and Ozguner F and Cesur G and Gokalp O and Mollaoglu H and Caliskan S and Delibas N.},
  title = {No effects of 900 MHz and 1800 MHz electromagnetic field emitted from cellular phone on nocturnal serum melatonin levels in rats.},
  year = {2005},
  
  url = {https://pubmed.ncbi.nlm.nih.gov/15986574/},
}
PubMed: 15986574

Cited By (24 papers)

Quick Questions About This Study

No, a 2005 study found that 30 minutes of daily cell phone exposure to 900 MHz and 1800 MHz frequencies for four weeks did not significantly affect nighttime melatonin levels in rats. Melatonin concentrations remained essentially unchanged between exposed and unexposed groups.
Research indicates these specific cell phone frequencies do not disrupt sleep hormone production. A controlled study measuring serum melatonin levels found no statistically significant differences between rats exposed to 900 MHz or 1800 MHz radiation and unexposed control groups.
According to this four-week study, even extended exposure periods may not affect melatonin production. Researchers exposed rats to cell phone frequencies for 30 minutes daily over four weeks and found no changes in nocturnal melatonin levels.
The study measured melatonin concentrations around 39 pg/mL in unexposed rats compared to approximately 35-38 pg/mL in groups exposed to 900 MHz and 1800 MHz radiation. These differences were not statistically significant, indicating no meaningful impact.
No significant differences exist between these frequencies regarding sleep hormone effects. The study found that both 900 MHz and 1800 MHz cell phone radiation produced similar results, with neither frequency significantly altering melatonin production compared to unexposed controls.