Artificial Illumination Can Affect More Than Your Mental Health

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Artificial Illumination Can Affect More Than Your Mental Health. As

Daylight Saving Time Comes to an End, What Happens to Our Internal Clocks?

 

By Rick Weiss

Washington Post Staff Writer

Tuesday, October 30, 2007; HE01

http://www.washingt onpost.com/ wp-dyn/content/ article/2007/ 10/26/AR20071026

02479.html

 

Oh, the light! The autumn light! Is there anything more glorious than an

October day, awash in the sun's low-slung amber rays?

 

And yet . . . perhaps you feel the dread, too. The looming inkiness that,

like the tide, crawls up your legs a little higher each day, turning that

honeyed light to molasses and molasses to muck until you realize, too

late, that the birds have left and the world has gone dark. Dark when you

wake up, dark when you go home.

 

In simpler times we slept more in winter, but modern living denies us that

luxury. So increasingly each day, soft-white lights from yonder windows

break -- along with halogens, tungstens and compact fluorescents. And when

we can't stand it anymore, we resort to manipulation, declaring that 6 in

the morning is now 5.

 

You got a problem with that, take it up in the spring.

 

Now science is finding that our manhandling of light and time is making us

sick.

 

Artificial illumination is fooling the body's biological clock into

releasing key wakefulness hormones at the wrong times, contributing to

seasonal fatigue and depression. And daylight saving time, extended by

Congress this year for an extra four weeks, risks dragging even more

Americans into a winter funk.

 

Much more than mental health is at stake. Women who work at night, out of

sync with the light, have recently been shown to have higher rates of

breast cancer -- so much so that an arm of the World Health Organization

will announce in December that it is classifying shift work as a " probable

carcinogen. "

 

That will put the night shift in the same health-risk category as exposure

to such toxic chemicals as trichloroethylene, vinyl chloride and

polychlorinated biphenyls (PCBs).

 

" Electric lights are wonderful, but as with a lot of other things, we

really mess things up, " said David Avery, a psychiatrist at the University

of Washington School of Medicine who studies light's impact on health.

" Our ancestors evolved in a very regular light-dark cycle, and our bodies

just work better that way. But more and more, we are creating very

irregular, erratic lighting cues. "

 

Researchers have long known that virtually all living organisms have

biological rhythms that are linked to light. But the human health

implications remained opaque until the 1970s, when scientists discovered

the brain's internal clock: the suprachiasmatic nucleus (SCN), a tangle of

neurons in the hypothalamus connected directly to the eyes.

 

The SCN controls the ebb and flow of hormones that influence sleepiness,

alertness and hunger. Prime among them is melatonin, levels of which rise

each evening, easing the onset of sleep, and then fall before dawn in

advance of awakening.

 

Rats whose SCNs are surgically removed become unhinged from time, sleeping

at odd intervals. And when one animal's SCN is transplanted into another's

brain, the recipient takes on the donor's wake-sleep schedule.

 

But the SCN does not work in a vacuum. It takes its cues from light

signals passed along by the eyes.

 

For decades scientists presumed that those clock-setting signals came from

rods and cones, the light-sensitive cells in the retina that provide

black-and-white and color vision. Then, in 2002, researchers at Brown

University discovered an entirely different set of light-detecting cells

in the eyes of humans and other mammals: ganglion cells.

 

Unlike rods and cones, ganglion cells specifically detect sky-blue light.

The amount of light needed to get them firing is about 500 billion photons

per second per square centimeter, or the intensity of sunlight reaching

the eye at about daybreak. Taken together, those traits make them the

perfect cells to tell the brain when dawn has arrived, which they do via a

dedicated neural conduit to the SCN.

 

Unfortunately, this system does not always work like clockwork.

 

Because of genetic differences, many people's clocks are set differently

from others'. In some, the evening melatonin spike is delayed and sleep

comes late. Early awakening is also often difficult for these night owls,

perhaps in part because their melatonin levels have not had time to drop

sufficiently by morning.

 

Others have the opposite problem: The clocks in these morning larks run

fast compared with solar clock time, lulling them to sleep early and then

awakening them well before dawn's early light.

 

Being out of phase with the natural day-night cycle can take a big toll,

causing fatigue, mood disturbances and depression. But for millions of

Americans, these symptoms become even worse in winter, blossoming into

what is in effect a months-long case of jet lag.

 

Scientists disagree on the cause of seasonal affective disorder, or SAD,

as it has come to be known. Some focus on winter's late sunrises, which

appear to push various hormone cycles out of phase with the daily

wake-sleep cycle. Others focus on the early sunsets, which may affect the

timing of melatonin production in the brain.

 

But while genes clearly play a role (night owls are more often affected),

location also matters.

 

Recent work by Thomas White of the New York State Office of Mental Health

and Michael Terman, director of the Center for Light Treatment and

Biological Rhythms at Columbia University Medical Center, has shown that

seasonal depression and mood disorders become more prevalent not only at

northern latitudes -- not surprising, as days are shorter there -- but

also toward the western edges of time zones, where people remain in

darkness almost an hour later each morning than their same-timed

counterparts farther east.

 

Daylight saving time, which has been stretched this year to Nov. 4 for a

number of reasons, including an effort to save energy, exacerbates the

problem by further delaying the time of sunrise, a key signal that resets

the body's clock each day.

 

" From the psychiatric perspective, the extension of daylight saving time

this year was a very bad decision, " Terman said. " Our expectation is we

will see increased depression and mood disorders. "

 

The good news is that treatments for seasonal depression -- primarily the

use of bright light, and in some cases melatonin supplements, to reset the

body's clock -- can be effective.

 

For most people with SAD, the trick is to get bright light exposure first

thing in the morning to simulate an earlier dawn and shift the body clock

forward, said Alfred Lewy, a psychiatrist and chronobiologist at Oregon

Health & Science University in Portland. For some people, taking 0.3 to

0.5 milligrams of melatonin in the midafternoon can also help, he added.

 

For the minority of SAD sufferers who are larks, light in the early

evening can help. (Some larks may also benefit from melatonin in the

morning, keeping in mind that even small doses can make some people

sleepy.)

 

Diagnosing yourself as owl or lark can be tricky. Wake-up times are

affected by much more than your natural clock (whether your sixth-grade

daughter has to be fed before trudging off to school in the dark, for

example), so your sleep schedule is not a surefire clue. Lewy suggests

trying morning light first, but switching to the lark regimen if symptoms

worsen.

 

Many kinds of lights are available for SAD treatment. Although some

experts recommend those rich in the sky-blue wavelengths (the color that

ganglion cells respond to), others warn that intense blue light can damage

the eye. Most research indicates that 30 to 90 minutes' exposure to

fluorescent " white " lighting of about 10,000 lux works fine, ideally with

a plexiglass diffuser to filter ultraviolet rays and dissipate glare.

 

So effective is light as a mood improver that many psychiatrists now

suspect that their understanding of depression has been backward: The

disturbed sleep and withdrawal into darkened rooms so often seen in

patients with depression, bipolar disorder and related problems may be not

a symptom of those diseases but a cause. Reset the clock, and the

depression lifts.

 

A 2005 review commissioned by the American Psychiatric Association

concluded that daily exposure to bright light was about as effective as

antidepressants against several forms of depression.

 

Recent studies have suggested that light therapy can also help patients

with Alzheimer's disease. " They have these random sleep and rest and

activity patterns throughout the day, " said Mark Rea, director of the

Lighting Research Center at Rensselaer Polytechnic Institute in Troy, N.Y.

When Rea and colleagues gave Alzheimer's patients daily doses of blue

light at about the intensity of a standard fluorescent bulb, the patients'

ability to sleep through the night was significantly enhanced.

 

Blue light also looks promising for its ability to induce alertness, said

Mariana Figueiro, a program director at the Rensselaer research center.

She is testing the light on submariners, who have trouble remaining

vigilant because their biological clocks don't get cued to dawn and dusk.

 

Of course, the fact that artificial lighting can reset people's clocks and

boost alertness at night speaks to its potential to throw normal rhythms

into disarray. As though it were not bad enough that lighting is a 24-7

feature of modern life, said Avery of the University of Washington, people

spend evenings staring at their " Microsoft blue " computer monitors, then

wonder why they can't fall asleep.

 

" We've deseasonalized ourselves, " said Thomas Wehr, a psychiatrist at the

National Institute of Mental Health in Bethesda. " We are living in an

experiment that is finding out what happens if you expose humans to

constant summer day lengths. "

 

The perfect solution, as any camper knows, is to give up artificial light,

an approach that quickly brings one into a cycle of long, restful nights

and easy awakenings at dawn. More realistically, experts recommend

avoiding bright lights after dusk and perhaps wearing yellow sunglasses at

brightly lit evening events to filter out the blue light that might fool

your ganglia into thinking it is morning.

 

For those working at night, " the idea might be to have a work environment

where at the beginning of the shift the lighting is heavier in blues that

suppress melatonin, then gradually it changes and becomes redder and

redder, " a hue that does not stimulate the eye's ganglion cells, said

Richard Stevens, an epidemiologist at the University of Connecticut Health

Center in Farmington.

 

Stevens knows how important night-shift lighting can be. It was his focus

on the issue that helped reveal that women who work night shifts for 20 to

30 years have breast cancer rates 30 to 80 percent higher than their

day-shift counterparts. The mechanism is still not fully explained, but

studies have since shown that melatonin -- whose secretion is suppressed

by nighttime illumination -- is a potent anticancer hormone.

 

Consistent with that, profoundly blind women also have very low rates of

breast cancer, presumably because their melatonin levels are never

suppressed by light.

 

A panel of experts convened this month by the International Agency for

Research on Cancer, part of the World Health Organization, reviewed

studies on animals that were kept awake at night or subjected to repeated

six-hour jet lags, and several large human studies of nurses and airline

flight attendants. It concluded there is strong evidence that shift work

can cause cancer.

 

The agency's pending declaration that shift work is a probable carcinogen

may not have immediate impacts, said Vincent Cogliano, who leads the IARC

Monographs program. " But our findings are looked at by government agencies

and scientific researchers and could stimulate additional studies. "

 

It may also send workplace lighting officials into a quandary.

 

" Should we use bluish lights in night-shift work to get the alertness, or

avoid it for its potential to cause cancer? " asked John Bullough of the

Rensselaer center, whose research has focused on the conflicting lighting

needs of hospitalized infants, who seem bothered by bright lights, and

their nurses, who need good lighting to see what they're doing.

 

The timing, color and intensity of light are not the only variables that

affect people's health. Several studies have found that the subtle flicker

common in fluorescent bulbs, especially older, low-frequency bulbs with

magnetic ballasts, can have detrimental effects, even though that flicker

is just below most people's threshold of conscious perception.

 

Stories that the flicker can trigger seizures are more legend than fact,

said Arnold Wilkins, director of the Visual Perception Unit at the

University of Essex in England. But fluorescent flicker can interfere with

eye muscle control while scanning text or images, he said, and can cause

eyestrain and headaches.

 

Flicker is not a problem with the new compact fluorescents, though some

are painfully heavy on glare. The real revolution in lighting, many

experts agree, is in the form of light-emitting diodes, or LEDs, which can

be tuned to any color. As they become more affordable, many say, light

will become a bona fide tool for manipulating health and mood.

 

Until then, people struggling to get through the winter will for the most

part be best off sinking obligingly into the long, gray flannel night and

avoiding the midnight lighting they think they crave.

 

Darkness doesn't have to be about depression and loneliness, said Dave

Crawford, executive director of the International Dark-Sky Association, a

Tucson-based nonprofit group that advocates against unnecessary

illumination.

 

It can be about stars, about contemplation, about quiet conversation with

a friend.

 

" If we sprayed water all over the place here in the desert, we'd be put in

jail. So why is it okay to spray light all over the place at night? " asked

Crawford, adding that more than half of all mammals spend most of their

waking hours at night or twilight, " including teenagers. "

 

Light is fine -- in the day -- Crawford said. " We're trying to bring to

everyone's attention that there is a night. "

 

For the next few months, that is going to be hard to forget. ¿

 

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