Motion sickness can occur when your brain can’t make sense of information from your eyes conflicting with what your inner ear is saying. This unpleasant experience is common enough, with most of us regretting reading a book in the car at some point in our lives. A similar pattern may also play out when our brains can’t make sense of our circadian rhythm, our natural daily cycle most commonly associated with our sleep schedule. There’s growing concern with people not getting enough sleep, or not sleeping when their circadian rhythm wants them to, but this new hypothesis goes further— misaligned circadian rhythms may be enough to cause health problems, regardless of sleep habits.
This model, called “circadian-time sickness,” is anchored in how the brain streamlines our experience in the world. Our brains constantly take known information and make small predictions about the outcomes of current experiences, refining those predictions as new information comes in. For internal clocks in our bodies, there are expectations about when it’s time to call it a day, taking in internal cues from things like our food intake, and external cues from the amount of light outside. When those two indicators suddenly conflict, say thanks to changing time-zones or daylight-savings time adjustments, the brain may get thrown off kilter, leading to circadian-time sickness.
Suffering more than a shortage of sleep
Normally we think of these conflicts being played out in our sleep cycles alone. Misalignment of your daily schedule from your natural circadian rhythm can make it hard to get enough sleep, hurting reaction times and memory as activity in the frontal cortex diminishes the longer you’re awake. While brain areas like the amygdala can keep chugging along, seemingly dependent on a different internal clock, the outer layers of the brain seem to need refreshment from regular sleep.
Circadian-time sickness suggests that while sleep can make for a more functional frontal cortex, it doesn’t undo problems with a misaligned circadian rhythm. People getting seemingly normal sleep, but misaligned circadian rhythms, still seem suffer from various health concerns, including metabolic syndromes and memory problems. While people usually notice disruptions to sleep as the primary symptom of a circadian-rhythm disruption, this hypothesis suggests that frequent travelers or swing-shift workers (or nerdy science bloggers?) have more to worry about even if they’re still getting some shut-eye.
Source: Out-of-sync body clock causes more woes than sleepiness by Laura Sanders, Science News