Why older people drink less
2007-12-27 19:26
New York - Changes in nerve activity that occur during aging may help to explain why older adults drink less when thirsty than younger people, according to new research.
The elderly tend to be less satisfied from drinking water when thirsty which increases their risk of dehydration and heat illness on hot summer days.
In the new study, Australian researchers used brain scans to examine the underlying cause in the difference in drinking habits between younger and older men.
They studied 12 healthy men in their 60s and 10 men in there 20s. Each man received an infusion of saline to make him thirsty and then he drank as much water as he wanted.
The researchers said the older group drank half as much water as the younger group, despite having similar salt levels in their blood and a similar response in a region of the brain called the anterior cingulate cortex (ACC).
Previous research has shown that the ACC is activated in response to thirst. These latest findings suggest that, in older people, this response may be prematurely shut down.
"Our findings suggest that the brain activity in the anterior cingulate cortex that sub-serves our motivation to drink when thirsty more rapidly turns off in elderly people after they drink a small amount of water," Dr. Gary Egan, of the University of Melbourne in Australia said.
"This explains why older people drink less even though they have achieved a similar degree of thirstiness as younger people," he added in an interview.
The findings are published in the early online edition of the Proceedings of the National Academy of Sciences.
Since the brain response to thirst was similar in younger and older men, the researchers suggest that age-related changes in the nerves supplying the brain may be at work.
Egan said that as people age there may be changes in the input from nerves in the mouth, throat and stomach that sense how much water we've consumed.
According to the researchers, older adults should be careful to drink enough water on hot, humid days or when they are exercising - possibly taking scheduled water breaks instead of relying on their thirst signals.
"The finding is particularly relevant to ensuring that older people drink regularly and in sufficient quantities, particularly during hot periods," Egan said.