April 11, 2011 -- Elderly people's reputation as early birds may have a biological and potentially treatable cause.
A new study suggests that sleep problems associated with aging, such as going to bed and waking early, may be caused by hormonal changes.
Researchers say if further studies confirm these results, some sleep problems among the elderly may eventually be treatable with drugs.
Although a person's daily circadian or sleep/wake rhythm is controlled by the brain, researchers say its mechanism is encoded by circadian clocks operating in nearly every cell of the body.
In the study, researchers compared the internal circadian cycles of skin cells taken from both elderly and young donors in two different experiments.
When both sets of skin cells were grown in bovine serum, a standard nutrient solution used by researchers to culture cells in the lab, there were no differences in their circadian rhythms.
But when the skin cells were cultured in human serum taken from older donors, the circadian rhythms shifted in the same manner seen among the elderly.
Researchers say the results suggest that changes in hormone levels circulating in the blood of older adults may play a role in early bedtimes and waking times, as well as other sleep problems commonly seen among the elderly.
"Our results suggest that hormonal changes can alter cellular clocks and these changes in turn might underlie the differences in circadian behavior caused by aging," write researcher Lucia Pagani, of the University of Zurich, Switzerland, and colleagues in the Proceedings of the National Academy of Sciences.