I guess this should have been obvious to me but I'm just not that intelligent, but being blind and having no exposure to natural light really throws off the body's natural circadian rhythms. Talk about life not being fair. So if you're reading this and are having trouble falling asleep at night, at least be thankful that it is somewhat under your control.
The good news, depending on your feelings about big pharma, is that pending FDA approval it looks like they might have a drug to help synchronize the body with a more natural 24 hour sleep cycle.
Quote from the Boston Globe
“A rare condition called non-24 sleep-wake disorder, or “non-24,” characterized by a body clock that is out of synch with the 24-hour cycle of the Earth day, can affect those with normal vision, but it especially plagues the totally blind who can’t perceive light. Of approximately 100,000 totally blind people in the United States, anywhere from 55 percent to 70 percent of them may suffer from non-24, according to Harvard neuroscientist Steven Lockley.”
A more in depth article from the Non-24 website
“The master body clock synchronizes your circadian rhythms
William, age 41: “I go to bed at 8, only to wake up two hours later. Then, in the afternoon, my body tries to shut down.”
The body clock is your natural timing mechanism, and for most people, sighted or blind, it runs a little longer than 24 hours. Thus, it's a non-24-hour clock. For some, it runs just a few minutes longer, and for others it runs much longer. The reason for this is not known.
For example, if your body clock is 24.5 hours, today you're running a half hour behind. Tomorrow you're an hour behind, and so on, until your natural rhythms have you sleeping during the day and awake at night. This continues and eventually your sleep-wake cycle briefly syncs up with the typical day-night cycle. Then it begins to move out of sync again. Some people experience a full circadian cycle as short as one and a half months. For others, it can be several months before their sleep-wake cycle is realigned with the 24-hour day.
The eye has two functions: to allow us to see images and to take in light. This light then signals the time of day to the brain. In people who are sighted, the non-24-hour master body clock is reset every day to 24 hours in the same way that hands on a clock can be reset. This ensures that the circadian rhythms synchronize to the typical day-night cycle.
For people who are totally blind, there are no such light cues. The body clock is left to run its natural course, with extra minutes adding up day by day until your circadian rhythms are essentially upside down from a typical 24-hour day.
Circadian rhythms are your body's tide. They control its natural ebb and flow. They keep its daily activity in sync with the 24-hour day, controlling the release of the hormones, melatonin and cortisol. When you get sleepy during the day, it's because melatonin is released, preparing your body for sleep. When you're unable to sleep, it's because cortisol has been released, telling your body when to wake and when to eat, among other things.
Melatonin, the hormone that controls sleep and mood, is usually released in the evening. But in someone with Non-24, it could be released in the middle of the afternoon if his or her cycle at that point is opposite the typical day. Cortisol, the hormone that controls your metabolism, cardiovascular function, immune system, and appetite, is usually released in the morning. But in someone with Non-24, it might be released in the evening, disrupting the body's natural progress toward sleep.”
This is how having circadian rhythms that are out of sync with the 24-hour day can impact the natural ebb and flow of the body.