When old mice experienced artificial jet lag, their death rate increased, scientists report.
Gene Block of the University of Virginia in Charlottesville and his colleagues study how the body's natural timekeeping, or circadian rhythm, changes with age. Several years ago, the researchers noticed that a surprisingly large fraction of their elderly lab rats died soon after researchers changed the daily cycle of light and dark in rooms containing the animals' cages.
To examine this phenomenon in more detail, Block's team worked with middle-aged and elderly mice. Some of the animals lived in cages where the researchers shifted daytime forward every week by turning the lights on 6 hours earlier, the equivalent of a person flying from the East Coast of the United States to France. The researchers shifted daytime backwards once a week by the same amount for other mice. A third set of mice didn't experience any schedule shift.