Sleep is a complex and important physiological function that occupies more than one-third of our life!
Sleep has two stages called non-rapid eye movement (NREM) and rapid eye movement (REM) alternate as you sleep.
Stages of sleep
Introduction to sleep: brain activity begins to slow down, muscles start to relax, and you can be easily woken up at this stage.
Beginning of sleep: further slowing down of brain and muscle activity, including a decrease of heart rate and body temperature.
Slow wave sleep (SWS): brain and muscle activity decrease significantly to allow for deep sleep
At this stage, dreaming occurs. Muscles of the body are paralysed, except muscles of the heart and lungs.
A study published in the Sleep Journal assessed if modest sleep restriction from 8 to 6 hours/night over 7 days is enough to cause impaired functioning young, healthy adults.1
The study recruited 25 young and healthy volunteers, aged 19-34 yr.1 They were studied over 12 consecutive nights in a sleep laboratory. The participants were allowed to sleep a total of 8 hr for the first 4 consecutive nights (10:30 pm – 6:30 am). During the subsequent 8 nights, the participants have awakened 2 hr earlier (10:30 pm – 4:30 am). The participants were instructed to continue on their normal daily routine/diet and to strictly refrain from consuming any caffeinated beverages and not to nap. Blood sampling was performed after day 4 and day 12. Sleep was monitored with ECG, electrooculography and electromyography.
Blood tests after 7 days of modest restricted sleep showed elevation in plasma TNFα (tumour necrosis factor alpha, which is involved in inflammation) and a drop in the maximum cortisol (hormone that regulates stress and low-glucose concentration) value only in males.1
“Women appear not only to sleep better but that they also can cope better with sleep loss/sleep disturbance in terms of inflammation markers, which, in part, may contribute to women’s lower cardiovascular risks and greater longevity.”1
The study found that modest sleep restriction from 8 to 6 hours/night over 7 days is enough to cause impaired psychomotor performance, increased secretion of proinflammatory cytokines, and decrease levels of cortisol. Interestingly, Mr Vgontzas and his co-researchers also found:
“Women appear to be more resilient to some extent than men to the effects of sleep loss.”