Elderly mice subjected to changes similar to those of jet lag and working irregular shifts had shorter life spans than other elderly mice, say researchers from the University of Virginia, USA.
You can read about this study in the journal Current Biology.
In this study the researchers wanted to see how old and young mice responded to changes in their usual day and night rhythms (circadian rhythm). One group of mice had their clocks put forward by six hours each week, while the other group had their clocks put back by six hours each week. A third group of mice experienced no time changes.
The mice whose clocks went forward each week effectively had their nights shortened, while those whose clocks went back each week effectively had their nights lengthened.
The scientists found that:
— The young mice were not affected
— Just 47% of older mice whose clocks went forward each week survived
— 68% of older mice whose clocks went back each week survived
— 83% of older mice whose clocks did not change survived
— Daily corticosterone levels were not affected in any of the older mice (corticosterone levels are linked to stress, which is said to cause ill health)
So, if the stress hormone, corticosterone, was not raised, what was affecting the health of the older mice? The scientists believe it was either lack of proper sleep or altered immune systems.
Team leader, Dr Gene Block, wrote “Whatever the precise mechanism, this raises important issues about the safety of counter-clockwise rotating shift work and the potential long-term health consequences for airline crews regularly crossing time zones.”
“Chronic jet-lag increases mortality in aged mice”
A.J. Davidsona, M.T. Sellixa, J. Daniela, S. Yamazakia, M. Menakera and G.D. Blocka
Current BiologyVolume 16, Issue 21 , 7 November 2006, Pages R914-R916
doi:10.1016/j.cub.2006.09.058
Click here to view abstract online
Written by: Christian Nordqvist
Editor: Medical News Today