Jewish World Review Feb. 22, 2002 /10 Adar, 5762

Lowering body temperature after heart attack improves outcome

By Robert A. Wascher, M.D., F.A.C.S. -- PEOPLE who sustain a heart attack and experience the loss of heart function outside of the hospital have a very poor chance of survival. The likelihood of surviving cardiac arrest without serious brain damage is even lower still.

Early experience with open-heart surgery showed that reducing the body temperature of a patient can significantly decrease the risk of brain injury caused by the loss of oxygen delivery (hypoxia) to the brain. Animal studies of artificially induced cardiac arrest have also shown an impressive reduction in subsequent brain injury, and death, in animals that were cooled down after their hearts were stopped. However, the applicability of these findings to humans has largely been left unexplored.

This week's New England Journal of Medicine includes a study, performed in Australia, of 77 patients who were brought into the hospital following cardiac arrest. After resuscitating the patients and restarting their hearts, 43 of the patients' bodies were cooled to 33 degrees Centigrade (normal body temperature is 37 degrees) for a period of 12 hours. The remaining 34 patients did not undergo hypothermia (cooling) treatment.

The researchers found that 49% of the hypothermia patients survived and had minimal or nor brain damage secondary to their cardiac arrest. On the other hand, only 26% of the patients who did not have their bodies cooled survived with good neurological function.

After statistical analysis, the researchers concluded that the lowering of body temperature increased the chance of surviving a cardiac arrest with a good neurological outcome by more than five-fold. The relatively small number of patients in this study will mandate larger studies before any changes can be proposed in the current treatment of patients with out-of-hospital cardiac arrest.

However, if this study's results hold up after larger scale studies have been performed, then it is very likely that hypothermic treatment will, someday, become part of the standard treatment in such cases.


Recently, the Archives of General Psychiatry published an interesting study suggesting that people with chronic mild sleep deprivation may live longer than people who sleep 8 or more hours per night. More than 1 million volunteers took an American Cancer Society survey in 1982, and were asked, among other questions, to describe their sleep habits, sleeping pill usage, and frequency of insomnia.

Six years later, the survey answers were correlated with the death rate of the study participants. The study's authors concluded that people who slept more than 8 hours per night, or 6 or less hours per night, had a shorter lifespan than people who slept 6 to 7 hours per night.

The risk of earlier death was most significant among volunteers reporting more than 8.5 hours of sleep per night and those who slept for less than 3.5 to 4.5 hours per night.

This study was widely reported in the press last week as evidence that mild sleep deprivation could possibly prolong one's life, while the traditionally observed "8 hours a night" sleep rule was actually associated with earlier death. Although the study controlled for other common causes of early death (such as smoking, obesity, and exercise habits), it has several significant weaknesses in terms of the validity of its conclusions.

First and foremost, the study is based upon the self-reported sleep habits of study volunteers. This is a notoriously subjective way of obtaining data within a study, as participants often, consciously or subconsciously, "fudge" in their responses based upon their reading of the question (and their perceptions of the study's goals). In this case, the sleep-related questions in the survey were also incidental to the primary goals of the project, and were not designed to detect subtle variations in the volunteers' sleep cycles.

There are many other reasons why people who sleep, on the average, less than 8 hours a night might live longer than those who sleep longer. Other factors that may be associated with less time available to sleep (such as marital and family responsibilities, demanding careers, more time dedicated to recreational or exercise activities, or to reading at night before turning in) have been linked, directly or indirectly, with a lower overall risk of early death.

Thus, the apparent association between mild sleep deprivation and increased longevity may have nothing to do at all with the actual number of hours of sleep one gets each night. At the same time, chronic sleep deprivation has been previously associated with depression, chronic fatigue, increased interpersonal conflicts, and impaired immune response to disease.

The point of this study may be somewhat moot in the United States, however, with recent surveys suggesting that the average American gets only about 6 hours of sleep per night anyway.

Still, the widespread publicity received by this study is a reminder that all research papers need to be critically evaluated before accepting the conclusions reached by their authors. In any case, the study does suggest that mild sleep deprivation is probably not especially harmful to one's longevity, although it sure does make me grouchy sometimes.

Certainly, married folks who are often irritable from chronic sleep-deprivation could find the consequences of such recurrent bouts of grumpiness to be "less than healthful" when they are at work, or at home with their also-harried spouses. Now there's an idea for an interesting study....

JWR contributor Dr. Robert A. Wascher is a senior research fellow in molecular & surgical oncology at the John Wayne Cancer Institute in Santa Monica, CA. Comment by clicking here.


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© 2002, Dr. Robert A. Wascher