Circadian rhythm is the term used to describe the cyclical phenomenon commonly known as “the body’s internal clock”. The human body experiences regular physiological changes over a period of roughly 24 hours (some researchers claim a 25-hour period): body temperature, sleep, hormonal and mineral levels, physical coordination, emotional state, mental acuity, etc.
Various studies have concluded that a part of this rhythmic change involves the capacity of the body to absorb alcohol. One study, for example, compared subjects consuming alcohol at 10:00am and 10:00pm, and found that the morning consumption resulted in earlier and higher peak concentrations of blood-alcohol. Lakatua, et al., “Observations on the Pharmacokinetics of Ethanol”, Ann. Rev. Chronopharmacology 297 (1985).
One of the top blood-alcohol testing experts in the field, Professor Kurt Dubowski of the University of Oklahoma, has confirmed that the time of day when an alcoholic drink is consumed may affect both the absorption rate and the peak concentration time (time and quantity). Dubowski, “Absorption, Distribution and Elimination of Alcohol”, 10 J. Stud. Alcohol 98 (1985).
Obviously, the recognized effects of circadian rhythm add yet another variable to any attempts to estimate blood-alcohol levels when driving based upon blood-alcohol levels when tested. (See my earlier post, “Rising Blood-Alcohol Levels in DUI Cases”.)