iOS 9.3’s Night Shift

Glenn Fleish­man looks at why it may not help you sleep

iPad&iPhone user - - CONTENTS -

The Night Shift fea­ture in iOS 9.3 lets you ad­just the colour tem­per­a­ture of the dis­play, shift­ing away from blue spec­trums of light, in the pu­ta­tive in­ter­est of im­prov­ing sleep. But Ap­ple makes no prom­ises. On its web­site, Ap­ple notes, “Many stud­ies have shown that ex­po­sure to bright blue light in the evening can af­fect your cir­ca­dian rhythms and make it harder to fall asleep.” In iOS, the fea­ture is ex­plained with “This may help you get a bet­ter night’s sleep.”

In fact, this fea­ture likely will have lit­tle or no ef­fect on most peo­ple. Ap­ple hasn’t mis­rep­re­sented any of the sci­ence, but clin­i­cal work done to date doesn’t point a fin­ger right at mo­bile de­vices or even larger dis­plays. Night Shift also can’t re­move enough blue to make a dif­fer­ence if that colour is the cul­prit. And blue light may not be the trig­ger it’s been iden­ti­fied as. While re­searchers haven’t tested the new fea­ture yet, sev­eral fac­tors add up to at best a placebo ef­fect and a re­minder to power your­self down.

Ap­ple might have done bet­ter to cre­ate some­thing called Night Safe, an op­tion that would countdown the mo­ments un­til you’d be locked out of your hard­ware till morn­ing ex­cept for emer­gen­cies or go­ing through a te­dious over­ride process – a Do Not Dis­turb on re­verse steroids.

Jump­ing to the chase, if you’re ready to crash: If you want to sleep bet­ter, the al­most uni­ver­sal sug­ges­tion from both sleep and light­ing re­searchers is to turn off any screen two hours be­fore your planned bed­time. Some also rec­om­mend us­ing warmer light­ing through­out your house in sources you use in the later evening.

Why do you feel blue?

Our cir­ca­dian rhythm, a bi­o­log­i­cal cy­cle, reg­u­lates how our body func­tions and re­pairs it­self, although it’s com­monly as­so­ci­ated with sleep and wake­ful­ness. It’s roughly 24 hours for hu­man be­ings, and our bod­ies use a num­ber of cues to keep us on track. Get­ting out of sync can con­trib­ute to ill­ness), obe­sity, di­a­betes, and even an in­creased risk of can­cer.

Re­searchers have con­ducted stud­ies over decades that iso­late peo­ple from ex­ter­nal cues to see what a nat­u­ral cy­cle looks like, and how we sleep and wake. More re­cently, a lot of clin­i­cal and sur­vey work has looked into mea­sur­ing the ef­fect of light­ing: cy­cles of light and dark, light tem­per­a­ture, bright­ness, and other fac­tors.

A dis­cov­ery about 20 years ago helped make a con­nec­tion, the lim­its of which are still be­ing felt out. Many an­i­mals, in­clud­ing hu­mans, pro­duce the hor­mone mela­tonin across the cir­ca­dian cy­cle, but it’s sup­pressed to low lev­els dur­ing nat­u­ral wak­ing hours. As it gets dark, that sup­pres­sion abates, and mela­tonin pro­duc­tion helps us be­come sleepy and re­main asleep. (It has many other at­tributes, too, and other hor­mones have cy­cles that seem less tied to sleep.)

Mela­tonin pro­duc­tion starts ramp­ing up about two hours be­fore your body’s nat­u­ral sleep cy­cle

would start – of­ten de­scribed in re­search as about 10pm. And it’s pro­duced in the largest quan­ti­ties in the wee hours, wher­ever in the world you are, right in the mid­dle of what your body per­ceives as the dark­est time of day.

If you want to sleep bet­ter, the al­most uni­ver­sal sug­ges­tion from both sleep and light­ing re­searchers is to turn off any screen two hours be­fore your planned bed­time.

Since this light re­cep­tor type was dis­cov­ered, sci­en­tists have con­nected in many, many stud­ies not just light and mela­tonin sup­pres­sion, but specif­i­cally light that’s heavy on blue fre­quen­cies. Blue light can os­ten­si­bly off­set the cy­cle of hor­mone pro­duc­tion by a cou­ple of hours or more. This has led to spec­u­la­tion that star­ing at tele­vi­sion sets, mon­i­tors, and mo­bile dis­plays dis­rupts or de­lays sleep. If you have to get up or are wo­ken up at a fixed time, as for most peo­ple, this both re­duces sleep and throws off the body’s en­docrine and other sys­tems.

Day­light has a large pro­por­tion of short-wave­length light at the blue end of the spec­trum (around 460 nanome­ters). In­door light­ning has been tra­di­tion­ally ‘warmer’, or to­wards the yel­low, longer-wave­length end (about 555nm) or red at the far end (650nm). That’s true of fire and most in­can­des­cent light­ing.

But a shift in light­ing over decades has shifted to­wards cool, ‘white’, or ‘day­light’ il­lu­mi­na­tion, whether in­can­des­cent, flu­o­res­cent, or LED. While thought of as whiter, they ac­tu­ally pro­duce bluer light, re­sem­bling more closely our per­cep­tion of a sun­lit day.

This de­scrip­tion of colour gets la­belled colour tem­per­a­ture, and is mea­sured in kelvins (K). On one end of the spec­trum, you have red/ yel­low can­dle­light at 1000K, con­sid­ered very warm; at the other end, pure blue sky is 10,000K, con­sid­ered very cool. Most LCD mon­i­tors and mo­bile dis­plays can cal­i­brate against a stan­dard called D65, which cen­tres at 6500K, blue and cool – it’s de­scribed as out­door day­light at noon. Many dis­plays are tuned or de­fault to a higher tem­per­a­ture, though, and are much bluer.

Spe­cific re­search and rea­son­able spec­u­la­tion cen­tres around how pre­dom­i­nantly blue light from tele­vi­sion sets, com­puter mon­i­tors, lap­top dis­plays, and mo­bile screens might be con­nected with the in­crease of a host of ail­ments in na­tions in which a large per­cent­age of res­i­dents use those tech­nolo­gies be­fore and at bed­time.

Of spe­cial in­ter­est is the sim­ple lack of sleep. The Cen­ter for Disease Con­trol and

Preven­tion es­ti­mates 50 to 70 mil­lion US adults have dis­or­ders that pre­vent them from sleep­ing suf­fi­ciently to be alert, pro­duc­tive, and rested on an av­er­age day.

All the dis­cus­sion of blue light has led to pro­grams and ex­ten­sions for many com­puter plat­forms that at­tempt to re­duce the pro­duc­tion of blue light in or­der to avert cir­ca­dian rhythm dis­rup­tion. The f.lux soft­ware ( just­get­flux.com) is a well-known ex­am­ple, avail­able for OS X, Win­dows, Linux, and rooted An­droid phones. (It could be in­stalled through a work­around in iOS, un­til Ap­ple asked f.lux to stop dis­tribut­ing it.)

iOS’s Night Shift is just the lat­est en­trant for colour-tem­per­a­ture shift­ing, al­beit mak­ing it avail­able to roughly 500 mil­lion de­vices via iOS 9.3. Only de­vices re­leased start­ing in about 2013 have hard­ware that sup­ports the fea­ture, ac­cord­ing to Ap­ple’s fea­ture notes.

But the big prob­lem is that there’s no solid ev­i­dence that mo­bile screens’ colour tem­per­a­ture is the real cul­prit, nor whether de­vices and mon­i­tors can shift enough to mat­ter if they were – or even if blue light on its own is the trig­ger.

Blue mean­ings

While ex­po­sure to colours of light has been well re­searched, it’s not en­tirely clear that merely see­ing light heavy in the blue part of the rain­bow is the trig­ger – or at least the sole trig­ger. It may be that a shift in colour in the hours around twi­light, which comes with a change from blue to yel­low, could be a more sig­nif­i­cant marker. Blue may be a red her­ring.

It might also be the in­ten­sity of light or the pro­por­tion of the vis­ual field it oc­cu­pies. A large, bright screen that’s far away could have as lit­tle or the same ef­fect as a small, bright screen close up. Many of the stud­ies un­til re­cently used full-room il­lu­mi­na­tion or specif­i­cally-tuned light sources (like pan­els used to treat sea­sonal af­fec­tive dis­or­der), and have taken place in highly con­trolled lab­o­ra­tory en­vi­ron­ments that block all other light. Be­cause of the cost and com­plex­ity of the ex­per­i­ments, the most rigidly con­structed ones of­ten in­volve only a dozen or so in­di­vid­u­als who spend sev­eral days un­der ob­ser­va­tion.

In terms of size and bright­ness, it’s more likely that an ef­fect on mela­tonin pro­duc­tion would come from ad­just­ing an iPad Pro than an iPhone of any size, due to light and in­ten­sity of light pro­duced.

Mar­i­ana G. Figueiro, a pro­fes­sor at Rens­se­laer Polytech­nic In­sti­tute and the pro­gram di­rec­tor of its Light­ing Re­search Cen­ter (lrc.rpi.edu), says her group has used pre­cise mea­sure­ments of light sources and dis­plays to cal­cu­late pre­dicted ef­fects and per­formed clin­i­cal test­ing to test out­comes.

She notes there’s a huge vari­a­tion be­tween an iPhone, a tablet, and large-screen tele­vi­sions. “Peo­ple tend to have a mis­con­cep­tion that be­cause it looks bright, be­cause your vis­ual sys­tem is so sen­si­tive, that it is af­fect­ing your mela­tonin,” she says. Her work and that of oth­ers has shown that you “can still sup­press mela­tonin with a warm colour if it’s a high light level.”

Even what’s be­ing dis­played mat­ters. Dr. Figueiro says a Face­book page with a white back­ground and mostly text pro­duces more light than the same

page viewed with white on black text. Although she hasn’t tested Night Shift yet, she says that in terms of size and bright­ness, it’s more likely that an ef­fect on mela­tonin pro­duc­tion would come from ad­just­ing an iPad Pro than an iPhone of any size, due to light and in­ten­sity of light pro­duced.

But be­yond the vari­a­tion, there’s the de­gree of blue re­moval. Ray Soneira, the pres­i­dent of Dis­playMate, a com­pany that makes video­di­ag­nos­tic hard­ware and soft­ware, says that Night Shift and re­lated soft­ware doesn’t turn down blue spec­tra in the cor­rect range enough, thus not pro­vid­ing as­sis­tance even if true.

In the case of Night Shift and sim­i­lar sys­tems, he ar­gues that the blue com­po­nent would need to be en­tirely re­moved or re­duced sig­nif­i­cantly more than the sys­tems of­fer, which in turn would make the dis­play too yel­low for most peo­ple. He writes, “Just slightly re­duc­ing the blue, which is what most apps do, won’t ac­com­plish much, so the im­prove­ments peo­ple ex­pe­ri­ence are of­ten mostly due to placebo and their own con­scious mod­i­fi­ca­tion of their behaviour in us­ing dis­plays.”

In any case, Dr. Figueiro says sleep re­search shows there’s an ex­tremely im­por­tant and of­ten over­looked fac­tor that re­quires more dis­ci­pline than an au­to­matic colour-tem­per­a­ture ad­just­ment. “Dis­rup­tion of sleep is not just mela­tonin sup­pres­sion; it’s what you’re do­ing to your brain to keep it alert,” she says. She rec­om­mends turn­ing off all your screens two hours be­fore go­ing to bed. “Th­ese pro­grams help, but they don’t com­pletely re­move the pos­si­bil­ity of sup­press­ing mela­tonin.”

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