RENEE MONTAGNE, HOST:
Let's take a look now at a set of genes we all have inside us. They're called clock genes, and they keep our bodies on 24-hour cycles of energy and sleep. As NPR's Rae Ellen Bichell reports, a new study says these genes change their rhythm as we get older.
RAE ELLEN BICHELL, BYLINE: Ever notice the cat naps older relatives take in the middle of the day or that grandparents tend to be early risers? Colleen McClung did. She's a neuroscientist at the University of Pittsburgh School of Medicine. And she wanted to know what was going on in the brain that changes people's daily rhythms as they age.
COLLEEN MCCLUNG: When you think about the early bird dinner specials, you know, it sort of fits in with their natural shift in circadian rhythms.
BICHELL: McClung studies a set of genes everybody has that function as the body's clock.
MCCLUNG: There is a core set of genes that has been described in every animal, every plant all the way down from fungus to humans.
BICHELL: And they're the master controllers of a bunch of other genes that control everything from metabolism to sleep. They do it on a 24-hour cycle. When you woke up this morning, they told a gland in your brain to give a jolt of the stress hormone cortisol to wake up. Tonight, they'll tell a gland to spit out melatonin, a hormone that makes you sleepy.
MCCLUNG: You can think of them as sort of the conductor of an orchestra. So they're really the ones that lead the rhythm and make sure that all the other genes keep in time.
BICHELL: She says it's been known for a long time that people who are older have disruptions in these rhythms. Their orchestras seem to go off beat. But it isn't known why. So McClung and her colleagues looked at what genes were being expressed in the brains of about 150 people, some young, some old, immediately after death. And they found that as they get older, these core clock genes lose rhythm. That they expected.
MCCLUNG: But what was really surprising to us was that along with this loss of rhythmicity, we found a gain in rhythmicity of a different set of genes.
BICHELL: Those genes might be working like a backup clock, one that starts ticking when the main one becomes less reliable. If that's the case, it could be contributing to diseases that tend to set in later in life, a lot of which involve changes in the sleep cycle.
MCCLUNG: And we're particularly interested in a condition called sundowning, where people become agitated and irritable and anxious only in the evening. And this is usually in older people that have dementia.
BICHELL: McClung thinks their backup clock genes might not be kicking in right. To find out, she and her colleagues will first have to figure out what exactly those genes do. For that, they'll need more brains, mouse brains this time. Rae Ellen Bichell, NPR News.
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