The destruction of the body's
natural rhythms accelerated the growth of cancerous tumors in laboratory
animals.
In mice whose body clocks --
also known as circadian rhythms -- were disrupted, "the body's defense
system was apparently less able to control tumor growth, and others were
following up on recent reports that the disruption of the body clock of
those who perform shift work seems to result in a higher propensity for
cancer.
In half the mice in the experiment,
the researchers destroyed a part of the brain that controls the body's
natural rhythms, including sleep-wake cycles as well as body temperature,
hormone release patterns, immune response and metabolism. The remaining
"control" mice received mock surgery.
The mice with part of their
brains destroyed lost proper functioning of their body's natural rhythms,
remaining at a more constant level throughout the day and night.
Researchers then implanted
tumors into all of the animals, and monitored the animals for tumor growth
as well as long-term survival rates.
The investigators found that
the tumors grew two to three times faster in the animals whose rhythms
had been disrupted. Those animals also experienced a significantly worse
survival rate, living only 22 days after the tumor graft, compared with
26 days in the other group.
The study authors speculate
that the part of the brain that controls the circadian rhythms may play
a role in fighting off disease by its influence of the body's immune responses
or hormonal fluctuations.
Human health is at its best
when we have regular routines. This need is magnified in cases of chronic
illness, so regular schedules in patients are well advised.
The findings may also point
to ways that proper functioning of the body clock checks tumor growth.
Journal
of the National Cancer Institute May 1, 2002;94:690-697
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