This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Zipes, D. P. Search for Related Content PubMed PubMed Citation Articles by Zipes, D. P. Pubmed/NCBI databases Medline Plus Health Information Heart Diseases Related Collections Electrophysiology Acute coronary syndromes

(Circulation. 1999;100:1590-1592.)
© 1999 American Heart Association, Inc.

Editorial

Warning: The Short Days of Winter May Be Hazardous to Your Health

Douglas P. Zipes, MD

From the Krannert Institute of Cardiology, Indiana University School of Medicine and the Roudebush Veterans Administration Medical Center, Indianapolis.

Correspondence to Douglas P. Zipes, MD, Krannert Institute of Cardiology, 1111 W 10th St, Indianapolis, IN 46202-4800.

Key Words: Editorials • circadian rhythm • myocardial infarction • mortality

	Introduction

 
Almost all living organisms have evolved biological rhythms linked to the day-night or light-dark cycles of the sun. The impact of such rhythms that follow the time of day and season of the year on a variety of physiological functions in humans has been recognized for a long time. The internal oscillator, or control station regulating the body's circadian clock, is the suprachiasmatic nucleus (SCN), a tiny (70 000 neurons) structure situated in the hypothalamus.¹ Located above the optic chiasm, the SCN processes external signals, such as ambient light and inputs from the brain, to regulate a variety of cyclical functions, including body temperature, sleep/wake cycles, and secretion of hormones such as serum cortisol, melatonin, thyroxin, and vasopressin.² Ambient light can entrain the SCN, which then modulates physiological and pathophysiological processes. In fact, like modulated parasystole,³ a burst of light striking the photoreceptors in the morning can advance the SCN cycle, whereas a burst in the evening can delay the phase-response curve. In humans, the SCN sets the intrinsic 24-hour cycle accurately to average 24 hours and 11 minutes.⁴

In addition to daily modulation by the SCN, seasonal fluctuations in body rhythms occur. For example, plasma L-tryptophan and competing amino acids are significantly lower in the spring, changes that parallel seasonal variations in the prevalence of violent suicide and depression.⁵ The seasonal affective disorder syndrome (SADS) is a well-established entity characterized by depression during the winter months. Psychiatrists have treated SADS patients by exposing them to artificial light for . . . [Full Text of this Article]

This article has been cited by other articles:

				J. H. Shuhaiber, K. Goldsmith, and S. A.M. Nashef The influence of seasonal variation on cardiac surgery: a time-related clinical outcome predictor. J. Thorac. Cardiovasc. Surg., October 1, 2008; 136(4): 894 - 899. [Abstract] [Full Text] [PDF]

				D. E. Wallis, S. Penckofer, and G. W. Sizemore The "Sunshine Deficit" and Cardiovascular Disease Circulation, September 30, 2008; 118(14): 1476 - 1485. [Full Text] [PDF]

				J. H. Shuhaiber, K. Goldsmith, and S. A.M. Nashef Impact of Cardiothoracic Resident Turnover on Mortality After Cardiac Surgery: A Dynamic Human Factor Ann. Thorac. Surg., July 1, 2008; 86(1): 123 - 131. [Abstract] [Full Text] [PDF]

				T. Mohri, N. Emoto, H. Nonaka, H. Fukuya, K. Yagita, H. Okamura, and M. Yokoyama Alterations of Circadian Expressions of Clock Genes in Dahl Salt-Sensitive Rats Fed a High-Salt Diet Hypertension, August 1, 2003; 42(2): 189 - 194. [Abstract] [Full Text] [PDF]