RENEE MONTAGNE, HOST:
And here's some cold water from researchers for binge watchers getting heavy doses of shows like "Making A Murderer" and "Transparent." A new study shows too much binge watching, just like watching too much regular TV, is bad for your brain. NPR's Angus Chen reports.
ANGUS CHEN, BYLINE: I've had plenty of afternoons telling myself I'm going to watch just one episode of a show. Then, this comes on.
(SOUNDBITE OF TV SHOW, "SHERLOCK")
MARTIN FREEMAN: (As Dr. John Watson) There is a man in there about to die. The game is on. Solve it.
UNIDENTIFIED MAN: "Sherlock" continues.
CHEN: Well, how am I going to stop now? I can spend hours with my laptop streaming show after show. But hours of TV every day could be pretty bad for our brains. A new study suggests more than three hours of TV every day might slow our minds over the years. Doctor Kristine Yaffe at UC San Francisco checked in with over 3,000 people for 25 years. The study started when they were young adults. Every few years, the participants guessed how many hours of TV they watched. Then, when they were in their 40s and 50s, they all took three cognitive functioning tests - memory, focus and mental quickness.
KRISTINE YAFFE: Those adults who watched a lot of TV did more poorly on some of the cognitive testing.
CHEN: Yaffe thinks TV could be bad just because you're not moving. It's well known that exercise helps the brain. Psychologist Margie Lachman at Brandeis University says that makes sense. But what about all the other things we do where we sit still?
MARGIE LACHMAN: Things like reading, writing, doing computer work, doing puzzles, these have been shown to be beneficial for cognitive functioning.
CHEN: Yaffe's team didn't look at whether people were watching more thought-provoking content or something a little more mind-numbing.
YAFFE: So we couldn't really figure out different types of TV watching and parse out different types of TV that may or may not be more or less cognitively stimulating.
CHEN: In any case, the differences between the 40 and 50-years-old in the study who did and didn't watch a lot of TV is significant but pretty slim. That could change with age.
YAFFE: Would people 30 years later then develop greater differences? Could this then be a risk factor for actually frank dementia? We don't really know that.
CHEN: And Yaffe also doesn't know if lower brain functioning just leads to more TV watching. Still, she thinks maybe we can prevent our brains from slowing down as early as our 20s with some easy things, like turning off the TV and downloading something interesting to listen to on a run. Angus Chen, NPR News.