Too much sleep as harm­ful as too lit­tle, study finds

St. Thomas Times-Journal - - LOCAL NEWS - JEN­NIFER BIEMAN

Sleep­ing in late isn’t go­ing to make you any sharper dur­ing the day.

It might even make you as bad at rea­son­ing as some­one who got only four hours of shut-eye.

Re­searchers at Western Univer­sity crunched the num­bers from more than 10,000 sleep study par­tic­i­pants — the largest pro­ject of its kind in the world — and found get­ting too much sleep and sleep­ing too lit­tle equally ham­per brain-power.

“We were in­ter­ested to see, in a large sam­ple of peo­ple from around the world, how ev­ery­day sleep pat­terns re­late to brain func­tion,” study lead au­thor and neu­ro­sci­en­tist Conor Wild said. “There was an over­whelm­ing re­sponse when we launched the study.”

The study by Western’s Brain and Mind In­sti­tute con­firmed a long-held as­sump­tion: seven to eight hours of sleep each night is op­ti­mum for best brain per­for­mance. On brain puz­zles and games, peo­ple who slept more than that were just as im­paired as those who slept less.

More than 10,000 peo­ple around the world were in­cluded in the study, pub­lished in the jour­nal Sleep.

All par­tic­i­pants com­pleted a com­pre­hen­sive on­line pro­file, in­clud­ing de­tails not only about their sleep, but also their med­i­ca­tions, his­tory of de­pres­sion or anx­i­ety, age and ed­u­ca­tion.

They were also asked to com­plete an on­line cog­ni­tive as­sess­ment shortly af­ter wak­ing up.

The games and puz­zles tested a range of abil­i­ties in­clud­ing ver­bal rea­son­ing, in­hi­bi­tion, short-term mem­ory, spa­tial work­ing mem­ory and se­lec­tive at­ten­tion.

Re­searchers found the peo­ple who slept four hours or less per­formed cog­ni­tive tasks worse then their well-rested coun­ter­parts. The same was true for peo­ple who over-slept, pat­terns that held for peo­ple of all ages in the study.

Par­tic­i­pants’ rea­son­ing and ver­bal abil­i­ties were the two traits most af­fected by sleep du­ra­tion. Short-term mem­ory per­for­mance was rel­a­tively un­af­fected, the study found.

“It doesn’t seem to af­fect all brain func­tions equally. Peo­ple who didn’t sleep very much ac­tu­ally had no prob­lem re­mem­ber­ing things,” Wild said. “It’s peo­ple’s abil­ity to solve com­plex prob­lems and rea­son through things that seemed to be specif­i­cally im­paired by too lit­tle or too much sleep.”

The study par­tic­i­pants were se­lected from an ex­ist­ing pool of more than 40,000 who signed on to be part of the world’s largest multi-na­tional sleep study. The pro­ject was launched in June 2017 by Western re­searchers.

As for why over-sleep­ing and un­der sleep­ing ap­pear to lead to sim­i­lar brain­power slug­gish­ness, Wild said it needs to be stud­ied fur­ther.

“It’s kind of an­other thing we want to dig into a lit­tle bit more,” he said. “It could be an ef­fect of sleep in­er­tia. If you’ve ever had that feel­ing of hav­ing a re­ally deep, long sleep it might take you awhile to come fully out of that sleep.”

Study au­thors are plan­ning to look closer at the data col­lected and use it in fu­ture research projects.

“We have a re­ally rich data set here,” Wild said. “There are still some in­ter­est­ing things to be found. We have some more ideas of how to re­ally dig into this data set to test new hy­pothe­ses and gen­er­ate new ideas we can fol­low up with in the lab.”

Dr. Conor Wild

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