Did you know that your body’s “clock” and the 24-hour time
we live our lives to on a regular clock are different? To put it into the most
basic terms time runs on a 24-hour schedule and our bodies run on a 24.5 hour
schedule.
The body clock is your natural timing mechanism, and for
most people, it runs a little longer than 24 hours. Basically it is a non-24-hour
clock. For the sake of the discussion in this blog we will average it out to
the body clock running on a 24.5 hour cycle. Some people run a little less,
some run a little more, but the average is about a half hour longer than a
normal 24-hour cycle we use on our clocks.
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, cortisol, etc. 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, 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. However 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.