Geomagnetic disturbances are associated with reduced nocturnal excretion of a melatonin metabolite in humans

Neurosci Lett. 1999 May 14;266(3):209-12. doi: 10.1016/s0304-3940(99)00308-0.


The effects of geomagnetic disturbances on urinary excretion of the melatonin metabolite, 6-hydroxymelatonin sulfate (6-OHMS), were studied in conjunction with 60 Hz magnetic field (MF) and ambient light exposure in 132 electric utility workers. Geomagnetic activity was assessed using a local (equivalent amplitude or A(K), Boulder, CO) and global (average antipodal or aa) index. Personal exposures to 60 Hz MFs and light were obtained using data-logging meters. The relationship between geomagnetic activity and 6-OHMS was assessed with adjustment for age, light exposure, and month of participation. Mean overnight 6-OHMS excretion was lower on days when the 36-h A(K) or aa values exceeded 30 nT. A greater reduction in 6-OHMS excretion was observed when increased geomagnetic activity was combined with elevated 60 Hz MF or reduced ambient light exposures.

Publication types

  • Clinical Trial
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Circadian Rhythm / physiology*
  • Electromagnetic Fields / adverse effects*
  • Humans
  • Male
  • Melatonin / analogs & derivatives*
  • Melatonin / urine
  • Occupational Exposure*
  • Photic Stimulation


  • Melatonin
  • 6-hydroxymelatonin