The primary objective of the proposed study is to determine whether
exposure to a 60-Hz magnetic field in the home sleeping environment
produced by an electric blanket is associated with a decrease in
nocturnal urinary melatonin levels and an increase in nocturnal urinary
levels of luteinizing hormone (LH), follicle stimulating hormone (FSH),
and estradiol in a sample of healthy women of reproductive years.
Secondarily, this study is designed to investigate the relationship
between nocturnal urinary melatonin levels and nocturnal urinary levels
of LH, FSH, and estradiol, regardless of nighttime exposure to magnetic
fields. At least 180 women will be recruited as volunteers from the
Seattle metropolitan area. Eligible for participation will be any woman
between the ages of 20 and 45 who is a resident of King County, who has
not been previously diagnosed with breast cancer, who reports regular
menstrual periods, who is not taking oral contraceptives or hormone
preparations, and who normally sleeps with an electric blanket during
the winter months. This investigation will employ a cross-over design
which treats each participant as her own control. Data collection will
take place during the winter months, when an electric blanket would
typically be used and will involve a three month period for each
subject. The first month is designed to evaluate menstrual cycle
regularity. The second and third months are each comprised of a washout
period followed by either an exposure period (electric blanket use
beginning the day of ovulation through Day 7 post ovulation) or a non-
exposure period (no electric blanket use beginning the day of ovulation
through Day 7 post evaluation). Half the subjects will be assigned to
exposure followed by non-exposure while the other half of the subjects
will be assigned the reverse order, non-exposure followed by exposure.
Using commercial kits, ovulation will be determined for each month.
During Months 2 and 3, magnetic field levels will be characterized in
each subject's sleeping environment from Day 3 post ovulation through
Day 7 post ovulation, and nocturnal urine will be collected on Day 7
post ovulation. Urine samples will be assayed for the primary urinary
metabolite of melatonin, 6-sulphatoxymelatonin, and levels of LH, FSH,
and estradiol. Information on the subject's medical history, medication
use, and characteristics of the electric blanket will also be collected.
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