Beware the Nocturnal Predator

Beware the Nocturnal Predator

For many years now, asthma has been referred to as “The Nocturnal Predator” because of its tendency to exacerbate at night.  The traditional explanation given was due to our normal circadian variation in adrenal gland output.  Our adrenal glands produce two hormones that are an innate treatment for asthma: adrenalin and cortisone.  In fact, many of the pharmaceutical therapies for asthma mimic the body in that they contain forms of adrenalin and cortisone.

Our adrenal glands “wake up” about an hour before we do and release surges of adrenalin and cortisone until about 4 or 5 pm.  Then they “shut down” so we can be prepared for our sleep quietude.  It is this dramatic drop in adrenal output at night that can allow asthma and other allergies to exacerbate. For many years this physiology was felt to be the total story.  But science always moves forward and new research is showing that adrenal variation is just part of the equation.

One very new understanding is that in addition to our brains circadian clock, individual cells including the immune cells also have circadian clocks.  When these clocks are disrupted the immune cells do not function optimally and therefore are less able to respond to allergic threats or microbial (virus & bacteria) invasion.  As small a clock disruption as that which impacts many students: their school/work schedule versus their weekend schedule can lead to greater difficulty with allergies and infection.

For years, the phenomenon of “everyone getting sick” at the beginning of fall semester has been blamed on the gathering effect of the “herd” that had been separated during the summer.  Certainly, this still plays a role, but the clock paradigm is equally important.

This clock effect also helps explain why shift workers and people who travel one or more time zones distant tend to have more allergies and more infections.   When bed time versus wake-up times have been studied it turns out that wake-up time is the critical factor.  You didn’t hear it from me but tell your teenage children not to sleep in until noon on Saturdays.


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