More than just a recharge
For a long time sleep was seen as a means of “recharging” the body but a whole a spate of recent research is showing how limited and out of date this mechanistic view of sleep is. Every new piece of research is building a view of sleep that positions it as one of the most vital components of physical and psychological wellbeing.
Sleep and your heart
For example, a recent study published in the respected journal Sleep showed that sleep deprivation enlarged blood vessels and limited the vascular compliance. In other words, lack of sleep plays havoc with your vascular system. “Chronic sleep restriction or sleep deprivation could push the vasculature to critical levels, limiting blood delivery,” study author Derrick Phillips (Washington State University, Pullman, USA) writes. In turn this may lead to “metabolic deficits with the potential for neural trauma”. It is not all bad news though the researchers did find that the lower basal neural activity during recovery sleep could help the blood vessel compliance to recover.
The study looked at seven adult female rats. The researchers implanted cortical electrodes into the rats to measure their evoked auditory responses over a three day period. They then used 65 decibel clicks as auditory responses and these hemodynamic responses were measures using near infrared spectrophotometry across three differing wavelengths so that they could measure the changes in oxygenated and deoxygenated haemoglobin during differing sleep deprivation conditions.
They found that there was a dramatic reduction in the evoked hemodynamic amplitudes of the rats after 10 hours of sleep deprivation when this was compared to their response after no sleep deprivation. They also found that the rats showed a rise in steady state oxyhemoglobin when suffering from sleep deprivation and that this lasted for up to 10 hours afterwards.
Less cognitive function and motor skills
It was also found by the study “that vasodilation is larger for extended waking periods and can lead to blunted hemodynamic responses during initial recovery sleep”. This is seen as unsurprising as it is expected that sleep deprivation causes reduced or impaired motor skills and cognitive capacities.
Consequences for neuroimaging studies as well
These studies also have some serious consequences for the conduct of functional neuroimaging studies as the levels of sleep deficit at the time an experiment is performed may have a significant influence on the functional activation results. In particular they may cause problems with the results of neural imaging methods that measure the cerebral blood flow (CBF) or volume (CBV), including both functional magnetic resonance imaging and positron emission tomography.
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