How day­light sav­ing time can dam­age your health

Baltimore Sun Sunday - - NATION & WORLD - By Lind­sey Tanner

As clocks ticked to­ward the end of day­light sav­ing time, many sleep sci­en­tists and cir­ca­dian bi­ol­o­gists pushed for a per­ma­nent ban be­cause of po­ten­tial ill ef­fects on hu­man health.

Los­ing an hour of af­ter­noon day­light sounds like a gloomy pre­view for the dark win­ter months, and at least one study found an in­crease in peo­ple seek­ing help for de­pres­sion af­ter turn­ing the clocks back to stan­dard time in Novem­ber — in Scan­di­navia.

Here’s what sci­ence has to say about a twice-yearly rit­ual af­fect­ing nearly 2 bil­lion peo­ple world­wide.

Sleep ef­fects: Time changes mess with sleep sched­ules, a po­ten­tial prob­lem when so many peo­ple are al­ready sleep de­prived, says Dr. Phyl­lis Zee, a sleep re­searcher at North­west­ern Medicine in Chicago.

About 1 in 3 U.S. adults sleep less than the rec­om­mended seven-plus hours nightly, and more than half of U.S. teens don’t get the rec­om­mended eight-plus hours on week­nights. One U.S. study found that in the week fol­low­ing the spring switch to day­light sav­ing time, teens slept about 21⁄2 hours less than the pre­vi­ous week. Many peo­ple never catch up dur­ing the sub­se­quent six months.

Re­search sug­gests that chronic sleep de­pri­va­tion can in­crease lev­els of stress hor­mones that boost heart rate and blood pres­sure, and of chem­i­cals that trig­ger in­flam­ma­tion.

It has also been shown that blood tends to clot more quickly in the morn­ing. These changes un­der­lie ev­i­dence that heart at­tacks are more com­mon in gen­eral in the morn­ing, and may ex­plain stud­ies show­ing that rates in­crease slightly on Mon­days

af­ter clocks are moved for­ward in the spring, when peo­ple typ­i­cally rise an hour ear­lier than nor­mal.

That in­creased risk as­so­ci­ated with the time change is mainly in peo­ple al­ready vul­ner­a­ble be­cause of ex­ist­ing heart dis­ease, said Barry Franklin, di­rec­tor of pre­ven­tive car­di­ol­ogy and car­diac re­ha­bil­i­ta­tion at Beau­mont Health hos­pi­tal in Royal Oak, Michi­gan.

Stud­ies sug­gest that these peo­ple re­turn to their base­line risk af­ter the au­tumn time change.

Car crashes: Nu­mer­ous stud­ies have linked the start of day­light sav­ing time in the spring with a brief spike in car ac­ci­dents, and with poor per­for­mance on tests of alert­ness, both likely due to sleep loss.

The re­search in­cludes a Ger­man study pub­lished this year that found an in­crease in traf­fic fa­tal­i­ties in the week af­ter the start of day­light sav­ing time, but no such in­crease in the fall.

In­ter­nal clocks: Cir­ca­dian bi­ol­o­gists be­lieve ill health ef­fects from day­light sav­ing time re­sult from a mis­match among the sun “clock,” our so­cial clock — work and school sched­ules — and the body’s in­ter­nal 24-hour body clock.

Tick­ing away at the molec­u­lar level, the bi­o­log­i­cal clock is set by ex­po­sure to sun­light. It reg­u­lates func­tions such as me­tab­o­lism, blood pres­sure and hor­mones that pro­mote sleep and alert­ness.

Dis­rup­tions to the body clock have been linked with obe­sity, de­pres­sion, di­a­betes, heart prob­lems and other con­di­tions. Cir­ca­dian bi­ol­o­gists say these dis­rup­tions in­clude tin­ker­ing with stan­dard time by mov­ing the clock ahead one hour in the spring.

Pres­sure to change: In the U.S., day­light sav­ing time runs from the sec­ond Sun­day in March to the first Sun­day in Novem­ber. It was first es­tab­lished 100 years ago to save en­ergy. Modern-day re­search has found lit­tle or no such cost sav­ings.

Fed­eral law al­lows states to re­main on stan­dard time year-round but only Hawaii and most of Ari­zona have cho­sen to.

Roen­neberg and North­west­ern’s Zee are co-au­thors of a re­cent po­si­tion state­ment advocating re­turn­ing to stan­dard time for good, writ­ten for the So­ci­ety for Re­search on Bi­o­log­i­cal Rhythms.

“If we want to im­prove hu­man health, we should not fight against our body clock, and there­fore we should aban­don day­light sav­ing time,” the state­ment says.

Heart prob­lems:


Day­light sav­ing time ended at 2 a.m. lo­cal time Sun­day when clocks were set back one hour. Did you re­mem­ber?

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