If we all had body clocks that ran true to a 24 hour day, we probably wouldn't suffer from circadian rhythm disorders. But day lengths don't stay the same; they change seasonally (and we compound the problem with Daylight Saving-time changes). As a result, our body clocks have evolved in order to constantly adjust. 'Normal' body clocks tend to run a bit slow, about 24 ½ hours instead of 24.
This adjustment was perfect for the eons of time when we didn't depend on artificial lighting. When the nights were longer, our body clocks would naturally run a bit slow, so we would sleep in a little more each morning. As morning light increased with spring, the new light signal would speed up our body clocks and help us have increased energy during the longer spring and summer days.
You could say that circadian rhythm disorders are a by-product of the industrial age. As our lifestyles have become less seasonal and our workdays less dependent on sunlight, circadian problems have escalated. It has come to the point where we get up without the sun, go to bed long after dark and spend very little time outdoors, even in summer. Only a few decades ago we spent hours outside, while now we average less than 90 minutes outside each day, and only 21 of those minutes are considered effective.1 Ignoring these light/dark signals robs us of essential zeitgebers and confuses our body clock with conflicting signals.
Age and sex play a significant role in circadian rhythms. When we are younger, our rhythms tend to run slow, especially during puberty. As the body prepares for major growth changes, it releases more melatonin, and we tend to sleep more. Excess melatonin can further slow down or delay body clocks, which is why so most teenagers tend to sleep-in in the morning, and in many cases suffer from delayed sleep phase syndrome . Mary Carskadon at Brown University estimates that 95% of all teens show signs of delayed circadian rhythms. Dr. Carskadon and several leading chronobiologists recommend that Jr. High and high schools start later in the day.2 Because later school or work schedules haven't proved practical, dawn simulation and specialized light therapy are the most effective solutions for delayed circadian rhythms.
Three times more women suffer from circadian rhythm disorders as men. Women tend to notice problems earlier than men, and their symptoms progress quicker. As women mature however, their body clocks tend to advance (run too quickly), and women over 40 may experience early morning insomnia as a result. In terms of numbers, men start to catch up with women by the time they reach their 50's, however, men usually don't experience advanced circadian rhythm problems until their mid 60's. Most seniors struggle with advanced circadian rhythms and early morning insomnia.
Even when we get the proper light and darkness signals, our circadian rhythms can be thrown off by factors such as trauma from, accidents or surgery. Staying in bed for more than a few days or chronic illnesses can cause circadian rhythms to shift or malfunction.
Although we may not like to admit it, many circadian rhythm sleep problems are acquired from bad behavior. Over time, we teach our body not to sleep. We stay up or sleep in late-two of the most destructive activities for circadian rhythms that depend on consistency. We eat foods that disagree with us at night, and we even enjoy a drink, caffeinated beverages or smoke, oblivious to their destructive impact on our circadian rhythms. Worse yet, we turn to sleeping pills or herbal supplements to solve our problem when they only mask it and can lead to addiction.
Body clock problems are not temporary, and may require long term or even life-long vigilance. For example, someone with a delayed circadian rhythm will not be able to fix it by taking melatonin and going to bed early for a few nights. Those with body clock problems need much stronger light signals like light therapy, and they need to maintain a regimen for several months or years.
As we unlock the secrets of circadian rhythms, we are finding that some people are more vulnerable to body clock problems. For example, melanopsin has recently been identified as the main circadian photoreceptor. It may be that those with circadian rhythm problems don't have enough of these special receptors, and so they depend on stronger light signals than others.
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