Aging, Eyes and Our Circadian Clock: What's the Connection?

It's not every day that a news story about circadian rhythms shoots to the top of the "most read" list in a major newspaper. But that's exactly what happened with this story about how the aging of our eyes may affect our circadian clocks and, in turn, our overall health. This New York Times piece outlines research that is working to connect the aging of the eye with disruption to the functioning of the body's circadian clocks and the development of many of the chronic and serious health conditions that are associated with age.

Circadian rhythms -- our own internal biological "clock" -- govern our sleep-wake cycle and several other daily rhythms of the body. It's a complicated and finely-tuned system of hormonal and bio-chemical reactions that helps us live in rhythm with the 24-hour day, waking in the morning and remaining alert throughout the daylight hours, then sleeping and rejuvenating at night. A key component of our circadian system is the timed release of the "sleep hormone" melatonin. When our circadian clocks are functioning properly, melatonin levels rise during the nighttime hours, promoting sleep. Melatonin levels are suppressed during daytime hours as other hormones such as cortisol rise, helping to provide the alertness and energy we need to navigate our waking day.

Our bodies' circadian clocks, and the rise and fall of melatonin, are driven by exposure to light. And our eyes play a critical role in capturing that light and transmitting information to the part of the brain that governs our circadian clocks.

Scientists in recent years have discovered a group of cells in the retina of the eye that are triggered by light to communicate with the area of the brain that controls the circadian clock. Researchers have determined that these light-sensitive retinal cells communicate directly with the brain's suprachiasmatic nucleus. This small cell cluster, located in the hypothalamus, is responsible for controlling the body's circadian rhythms.

Our circadian clocks are incredibly precise and can be very sensitive to disruption:

Exposure to light at night. This happens most often these days through our ever-present electronic devices, which seem to be everywhere, including the bedroom. Falling asleep with the television on, leaving a cell phone, laptop or tablet on your bedside table -- the light emitted from these devices can throw your circadian rhythms out of whack and disrupt your sleep.

Age. Evidence has shown that the body's circadian clock functions less effectively as we age.

Shift work. People who work nights, or an irregular combination of day and night shifts, are frequently living at odds with their biological clocks. Firefighters, police, medical professionals, pilots and other shift workers -- as well as people who travel frequently across time zones -- suffer sleeplessness and other health problems as a result of disruptions to their circadian clocks.

Here's where the aging of the eye comes into play. As our eyes age, they become less effective at absorbing light. Pupils become narrower. The lens of the eye takes on a yellow cast. Overall, our eyes become less adept at absorbing light -- particularly blue light, the part of the light spectrum that has an especially powerful effect on the retinal cells that work with the brain to control circadian rhythm. This study showed how dramatically blue-light absorption decreases with age:

• The eyes of a 10 year old have 10 times the ability to absorb blue light as the eyes of a 95 year old.

• By age 45, a person's eyes are able to absorb only 50 percent of the blue light needed to keep circadian rhythms functioning properly.

Research into the effects of blue light exposure on the body's circadian rhythms reveals the negative consequences of the decrease in blue-light absorption that comes with age:

•In this study, women were exposed to blue light for a continuous 30-minute period. The younger women in the study responded to the blue light exposure with a drop in melatonin levels. Older women, exposed to the same amount of blue light, did not experience a suppression of melatonin levels.

•This research revealed that older men were significantly less affected by exposure to blue light than younger men when researchers measured for alertness and mood. Younger men experienced a boost in alertness and mood after exposure to blue light that older men simply did not experience.

What does all this fascinating science mean in practical terms? Exposure to light, especially sunlight, matters. And it matters increasingly as we age. As our ability to use light effectively decreases, we need to increase the amount of our exposure in order to help strengthen and boost our circadian rhythms. Keeping our eyes healthy and promptly treating eye problems such as cataracts is critical. The health of our eyes, it seems, may have a profound effect on the quality of our sleep and our overall health.

Sweet Dreams,
Michael J. Breus, PhD
The Sleep Doctor™
www.thesleepdoctor.com

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Comments

[habiger]

10:47 PM on 03/18/2012

I thought i died of skin cancer if I stayed in the sun to long. That ole saying, dam**d if you do and dam***d if you don't.

[prettyliars]

06:12 PM on 03/18/2012

is there any link to changes in blood pressure when the rhythm is disrupted?

[JohnSawyer]

06:11 AM on 03/18/2012

i wonder if some kind of anti-oxidant eye drop would help maintain the lens' ability to let blue light through it. Though the article isn't clear on whether the reduction in blue light absorption is strictly in the lens, or in the retina as well.

[leontherat]

02:47 PM on 03/12/2012

i was medical worker and worked nights for 30 years . i was also a sleep professional . have not worked nights for 3 years now and to this day i cannot sleep properly at night and would never go back to working nights for any amount of money. the more research that is being done shows more and more the bodies vulnerability to cancer, illness and sleep disturbances that have a long lasting impact. growing older is bad enough but to have that mon key on your back as well is just hard to recoup from if your even able to do so. shift differentials for night shift workers are definately not what they should be and need to be reevaluated by all companies required to staff at night.

[temmaleah]

02:34 PM on 03/12/2012

it's funnu. when i was younger and worked at the hospital i worked the 7-3:30 shift and when asked would do a double and work the 4-11:30 shitft with no trouble....but if i f and worked the mid shift of 2 -11:30 i had trouble functioning and really difficult.....then later on when i worked at hsn and wally world i worked the graveyard shift and i loved it.and so did my body....i think that when a job has shifts they need to let the employee choose their shift and not change it.....not if they want optimal job performance because people DO know their own body......

[Edwin Keever Jr]

10:26 AM on 03/12/2012

When I was younger I would wake up in the morning and there was one thing that was always stiff.
Now at my age, when I wake up in the morning that's the only thing that isn't stiff!

[items17070]

04:43 PM on 03/12/2012

TMI

[Edwin Keever Jr]

10:31 PM on 03/12/2012

That didn't really happen it was a joke. But if you want TMI, I ware glasses and when I was a kid my mother said to me: "I know what you are doing in that bathroom! If you keep doing it you'll go blind!" I said: "Mom, can I do it at least until I need glasses?"

[DickClark]

10:23 AM on 03/12/2012

.......................funny.....................

............. .I just logged on.............

........this was the first article I......
.......read on line this morning......
.......after sitting on our deck.......
.and enjoying my morning coffee.
......and my first, real sit- down....
................. in the sun..................
................for this year.................

.............I'm 71 years old.............

.................I'm smiling.................

[Myriah007]

09:49 AM on 03/12/2012

Aging----what a slow death trap

[rgrsjolly]

07:26 AM on 03/12/2012

Shift work is the most sadistic idea forced on the American worker. Fortunately, I only had to work on swing shift for a few years, but they were the worst years of my life.

[henery]

08:11 AM on 03/12/2012

You are right on that one. Shift work should be outlawed. There is no reason for it. Plenty of people would be willing to work the 1st 2nd or 3rd shift and stay on it. I was in the Military for 21 years and flew so that was like shift work, even though we had plenty of rest before and after each flight (except in war). After I got out I worked at a university. I picked 3rd shift and loved it.
In that same town my friend became Chief of police he changed the shift work. All officers picked their shift. Every one on that force loves it.

[fmb555]

09:49 AM on 03/12/2012

For 27 years I worked a schedule of 2-10 hour days (7a-5p) then off for 48 hrs followed by 2-14 hr nights (5p-7a) then off for 72 hrs. This schedule also moves what days you work one day each week. If I worked days Mon & Tue and nights Thu & Fri this week, next week I would work days Tue & Wed, nights Fri & & Sat. This just carried forward forever. I've been retired for 10 years now and still haven't been able to get my body to readjust to a normal or routine sleep schedule.

[ignacio sanabria]

11:30 AM on 03/10/2012

SAD: Seasonal Affective Disorder, a real disorder with strong health implications. A case in point: A Californian resident will behave totally different from an Alaskan resident. Both are human, but one gets more sunlight than the other.

[Graybeard47]

12:29 PM on 03/12/2012

Plus the one from Alaska is more intelligent!

[prawn259]

07:55 PM on 03/12/2012

Yeah, that's why he lives in an economically depressed state and voted for a quitter with no brains who claimed a seven time felon was her mentor, for governor. We won't even bring up the weather.

[Bucket-Of-Love]

02:53 AM on 03/10/2012

Dr. Breus, can you comment about what is known in regards to the use of light therapy from artificial sources (light boxes) as a means of positively impacting Circadian rhythms and health in general. Also, about what is known about light and DSPS.