Chapter 028. Sleep Disorders (Part 15)

Medical Implications of Circadian RhythmicityProminent circadian variations have been reported in the incidence of acute myocardial infarction, sudden cardiac death, and stroke, the leading causes of death in the United States. Platelet aggregability is increased after arising in the early morning hours, coincident with the peak incidence of these cardiovascular events. A better understanding of the possible role of circadian rhythmicity in the acute destabilization of a chronic condition such as atherosclerotic disease could improve the understanding of the pathophysiology.Diagnostic and therapeutic procedures may also be affected by the time of day at which data are collected. Examples include...
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Chapter 028. Sleep Disorders (Part 15) Chapter 028. Sleep Disorders (Part 15) Medical Implications of Circadian Rhythmicity Prominent circadian variations have been reported in the incidence of acutemyocardial infarction, sudden cardiac death, and stroke, the leading causes ofdeath in the United States. Platelet aggregability is increased after arising in theearly morning hours, coincident with the peak incidence of these cardiovascularevents. A better understanding of the possible role of circadian rhythmicity in theacute destabilization of a chronic condition such as atherosclerotic disease couldimprove the understanding of the pathophysiology. Diagnostic and therapeutic procedures may also be affected by the time ofday at which data are collected. Examples include blood pressure, bodytemperature, the dexamethasone suppression test, and plasma cortisol levels. Thetiming of chemotherapy administration has been reported to have an effect on theoutcome of treatment. Few physicians realize the extent to which routine measuresare affected by the time (or sleep/wake state) when the measurement is made. In addition, both the toxicity and effectiveness of drugs can vary during theday. For example, more than a fivefold difference has been observed in mortalityrates following administration of toxic agents to experimental animals at differenttimes of day. Anesthetic agents are particularly sensitive to time-of-day effects.Finally, the physician must be increasingly aware of the public health risksassociated with the ever-increasing demands made by the duty-rest-recreationschedules in our round-the-clock society. Further Readings Flemons WW: Clinical practice. Obstructive sleep apnea. N Engl J Med347:498, 2002 [PMID: 12181405] Pack AI et al: Risk factors for excessive sleepiness in older adults. AnnNeurol 59:893, 2006 [PMID: 16718691] Scammell TE: The neurobiology, diagnosis, and treatment of narcolepsy.Ann Neurol 53:154, 2003 [PMID: 12557281] Silber MH: Clinical practice. Chronic insomnia. N Engl J Med 353:803,2005 [PMID: 16120860] Bibliography Allen RP et al: Restless legs syndrome prevalence and impact: RESTgeneral population study. Arch Intern Med 165:1286, 2005 [PMID: 15956009] Arendt J: Importance and relevance of melatonin to human biologicalrhythms. J Neuroendocrinol 15:427, 2003 [PMID: 12622845] Ayas NT et al: Extended work duration and the risk of self-reportedpercutaneous injuries in interns. JAMA 296:1055, 2006 [PMID: 16954484] Barger LK et al: Extended work shifts and the risk of motor vehicle crashesamong interns. N Engl J Med 352:125, 2005 [PMID: 15647575] Barger LK et al: Impact of extended-duration shifts on medical errors,adverse events, and attentional failures. PLoS Med 3:2440, 2006 Berson DM et al: Phototransduction by retinal ganglion cells that set thecircadian clock. Science 295:1070, 2002 [PMID: 11834835] Cajochen C et al: Separation of circadian and wake duration-dependentmodulation of EEG activation during wakefulness. Neuroscience 114:1047, 2002[PMID: 12379258] Kamel NS, Gammack JK: Insomnia in the elderly: Cause, approach, andtreatment. Am J Med 119:463, 2006 [PMID: 16750956] Czeisler CA et al: Stability, precision, and near-24-hour period of thehuman circadian pacemaker. Science 284:2177, 1999 [PMID: 10381883] Czeisler CA et al: Modafinil for excessive sleepiness associated with shiftwork sleep disorder. N Engl J Med 353:476, 2005 [PMID: 16079371] Dijk D-J, Lockley SW: Integration of human sleep-wake regulation andcircadian rhythmicity. J Appl Physiol 92:852, 2002 [PMID: 11796701] Fantini ML et al: Idiopathic REM sleep behavior disorder: Toward a betternosologic definition. Neurology 64:780, 2005 [PMID: 15753409] Horowitz TS et al: Efficacy of bright light and sleep/darkness scheduling inalleviating circadian maladaptation to night work. Am J Physiol Endocrinol Metab281:E384, 2001 Kryger MH et al (eds): Principles and Practice of Sleep Medicine, 4th ed.Philadelphia, Saunders, 2005 Kushida CA et al: Practice parameters for the indications forpolysomnography and related procedures: An update for 2005. Sleep 28:499, 2005[PMID: 16171294] Landrigan CP et al: Effect of reducing interns work hours on seriousmedical errors in intensive care units. N Engl J Med 351:1838, 2004 [PMID:15509817] Lockley SW et al: Effect of reducing interns weekly work hours on sleepand attentional failures. N Engl J Med 351:1829, 2004 [PMID: 15509816] Lockley SW et al: High sensitivity of the human circadian melatoninrhythm for resetting by short wavelength light. J Clin Endocrinol Metab 9:4502,2003 ...