Not a Morning Person? Your Eye Color Could Be to Blame

Have you ever wondered what makes some of us sleepier than others? Why do some people seem to be able to jump out of bed first thing in the morning, while others struggle to get going? Part of the answer may lie in our eyes, or rather the color of our eyes. It turns out that iris pigmentation may have a great deal to do with how much sleep we get.

A recent study in the journal, Chronobiology International reveals that on average, those with darker colored eyes have a harder time getting up in the morning, and that their sleep cycles are as much as two hours behind those with lighter pigmentation.¹ When your body clock is behind or 'delayed,' it means you're not getting effective sleep, especially if you have to get up early (by 7 or 8 am ) every morning. In addition to cutting hours of precious sleep, delayed sleep cycles can also cause problems with sleep onset and late night insomnia.

Why Eye Color Makes a Difference

Tests show that iris color filters sunlight, and the darker the iris, the less sunlight gets into the eye. Sunlight is critical for healthy sleep/wake cycles, because our bodies use sunlight and darkness to know when to go to sleep and wake up. Those with lighter colored eyes perceive light later in the day and earlier in the morning, and these stronger signals of light reinforce a healthy daily sleep and energy pattern known as circadian rhythm .

Circadian (Sir Kadian) is Latin for 'about a day.' The control center in the hypothalamus, called the Suprachaismatic Nucleus, or 'body clock,' uses these signals to regulate everything from sleep to mood, energy and appetite. When the body clock doesn't get the right type of light at the right time of day it malfunctions, causing circadian related sleep disorders.

How Do Your Eyes Stack Up?

Those with light blue and gray eyes fared best in tests. Green and hazel eyes showed moderate sleep delays up to one hour. Those with brown, dark brown and black eyes, on average showed sleep delays of two hours.

How to Know if You Have a Circadian Sleep Disorder

Although eye color may play a part, other factors contribute to circadian related sleep disorders. If you lack energy during the day or feel more tired at a certain time, say morning or evening, or if you're awake or alert when you'd rather be sleeping, you may have a circadian related sleep disorder. Dr. Michael Smolensky, head of the American Association for Medical Chronobiology and Chronotherapeutics, estimates that most sleep disorders involve circadian rhythm problems and that circadian rhythms themselves account for 25% of all sleep disorders.²

Treatment

Since these sleep disorders result from the lack of light, the most effective treatment is received via specialized light at the right time of day. Most circadian rhythm disorders cause the body clock to slow down. Some body clocks react by speeding up too fast, or cause other abnormalities. In each case, specialized light is used differently, so knowing when to receive light is very important.

Circadian Rhythm Assessment

One way to know for sure is by taking the Circadian Rhythm Assessment. The assessment only takes a few minutes and can determine whether you have a circadian rhythm problem, the degree or severity of the disorder, and which type of disorder you may have. The assessment also plots your circadian rhythm over a normal one, and it calculates the best time for you to use light. This 'personal treatment schedule, is important, because everyone's body clock is different, and so the timing and amount of light will be different.

I get plenty of light, how can I have a Circadian rhythm disorder?

The problem isn't so much that we need more sunlight, but that we need light at certain tines of day. Where we don't get the right amount of light at those times, our body clocks start to break down. A recent national epidemiological study revealed some interesting things about our outdoor habits. The average American spends less frau 90 minutes outdoors, and only 21 of those minutes are in sunlight strong enough to affect our circadian rhythms, and it takes at least three hours per day of sunlight to positively affect our body clocks. By contrast, researchers now use specialized light to reset the body clock with only 10-1 5 minutes per day.

Good News

The good news about circadian related sleep disorders is that they are effectively treated with specialized light. Most people respond to light within a few days with complete response in a couple of weeks.

1. White, TM et al. Effect of Iris Pigmentation and Latitude on Chronotype and Sleep Timing, Chronobiology International. Vol 20/09/2003 . 1193-1194
2. Smolensky, M., Lamburg, L. The Body Clock Guide to Better Health. Henry Holt & Co. 2000. ppg.66-79