LACK of sleep could be worse for the body than we thought, at least if humans react to it in the same way as rats do.
Tarja Porkka-Heiskanen of the University of Helsinki, Finland, and her team discovered that rats seem to mount an immune response to sleep deprivation, producing molecules that ordinarily are associated with stress. This suggests that chronic sleep deprivation could lead to stress-related illness, such as heart disease, for example.
Porkka-Heiskanen鈥檚 team was studying how the brain triggers 鈥渞ecovery鈥� sleep to overcome the effects of sleep loss. Their earlier work in rats had shown that levels of nitric oxide increase in the basal forebrain during periods of sleep deprivation and that this plays a role in prompting recovery sleep.
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They had also found that an enzyme called nitric oxide synthase (NOS) was responsible for jump-starting the production of nitric oxide.
But where was the NOS enzyme coming from? Porkka-Hieskanen had expected that the NOS produced by the brain would be in a so-called 鈥渃onstitutive form鈥�, in other words, it would be made regardless of the need for it.
Instead, her team found that the NOS was in an 鈥渋nducible form鈥� (iNOS) which is usually produced when the body mounts an immune response to stress (European Journal of Neuroscience, DOI: 10.1111/j.1460-9568.2006.05019.x). 鈥淭his was a big surprise,鈥� says Porkka-Heiskanen. 鈥淚t means that the body experiences sleep deprivation as some kind of hostile threat.鈥�
The researchers also found that the rats began producing iNOS after being deprived of sleep for just 10 minutes. 鈥淪o even short periods of sleep deprivation are able to create this reaction,鈥� says Porkka-Heiskanen. 鈥淚f it becomes chronic, we are really putting a big strain on the body.鈥�
鈥淭he body experiences sleep deprivation as some kind of hostile threat, mounting an immune response as if to stress鈥�
There is no direct evidence to suggest that chronically high levels of iNOS are dangerous. But a 2004 study of healthy adults aged between 26 and 38, who had only 4.2 hours sleep for 10 consecutive nights, hints at the dangers. Levels of a molecule related to iNOS called C-reactive protein were raised in the volunteers 鈥� a strong predictor of heart disease.
