SLEEP AND YOUR HEART

We spend 7 hours a day sleeping, 49hours a week, 217 hours a month and 2,555 hours a year. In fact about one third of our lifespan is spent sleeping. Yet, for many many  years, we have not done much research to understand sleep and its importance. However, since the new millennium, much work has been done and we now understand sleep much better, especially its healing aspects for the body. How sleep is so very important for the body to rest, heal and restore itself.

SLEEP

Many of us go to bed ( to sleep ) at about 11-12 midnight and wake up at about 6-7am. Some a bit earlier, some a bit later. Do you know what happens between 11pm till 6am, when your eyes are closed? Much work has been done, using the EEG ( electro-encephalogram ) to study our brain electrical waves ( which tells us what is happening in the brain ), and video monitoring to correlate the brain waves with what is happening to the sleep subject, since they are both monitored simultaneously.

Using these sleep EEG studies,  we know that our body / brain undergoes 4 stages ( some say 5 stages initially, but have now combine stage 3 and 4 ) of differing brain activities. We call it stage 1, 2, 3 (these are non REM ) and Stage 4  REM sleep.
 

Stage 1 ( non REM ) sleep: Very light sleep, basically just getting into sleep. The subject is easily aroused and becomes orientated into their preceding activity quickly. There may be slight eye movements and muscle twitches. Basically light sleep in stage 1. This stage may last a few minutes only.

Stage 2 ( non REM ) sleep: Deeper sleep. The brain activity slows down with occasional burst of activity. The eye movements stops. The subject lapse into deeper sleep and begin to relax. This is quite obvious EEG wise as the brain activity slows down and have only occasional burst activity. Stage 2 can last half of the night sleep. The subject is now quite relaxed.

Stage 3 ( non REM ) sleep : The subject by now is fully relaxed and difficult to arouse.  They are fully relaxed. The brain activity is very slow now ( almost exclusively  delta waves ). It is as if the brain and body is hibernating. This is the stage where the body and mind is repairing itself after a difficult day.  This stage is absolutely essential for the body ( especially the heart ) and the mind. This is also the stage where bed wetting in children and sleep walking occurs. It is also during this stage that the body repairs and rebuilds  with secretion of hormones and immunological proteins.

REM sleep : This is the 4^th stage of sleep. We enter REM sleep about 60-90 mins after falling asleep. During this stage, brain activity increases and there is rapid eye movement ( that is where the name REM – rapid eye movement comes from ) . Our respiration becomes rapid and irregular, our heart rate becomes more rapid and our blood pressure rises.  This is when we have dreams and in many ways, we are temporary paralysed, and arousal is difficult. The EEG will show rapid slow waves. In the young, when the brain is still maturing, REM sleep allows for development of neuronal conduction and so maturity of the brain. Physiologically speaking, this is also when we consolidate all the happenings in the day and store them in the different compartments of our brain. This is also when the body.

During sleep, we progress cyclically from non-REM 1,2,3 to REM almost at 60-90 min cycles. As the night progresses, the REM portion gets longer and the non REM portion gets shorter. By early morning, when we awake, it I usually from the REM portion of sleep. Basically, the non Rem 3 phase allows for rest and repair of bodily functions stressed during the day and the REM portion restores and consolidates the activity of the previous day. In the young and immature, REM sleeps also allows for maturation of the CNS. All these activities of course involve  hormones and immune system responses.

Every night, over a 7-8 hours sleep, there are about 5 cycles of non REM / REM sleep.
 

The Heart

The heart is a vital active organ of the body and it  is continually working, pumping life giving blood to the whole body. It never rest. When we are stressed, it is also stressed. So whenever the body rests, the heart has a chance to take things easy and “rest”.  Meaning that it reverts to basal functions, just enough to sustain life. Of course it never stops. This “rest” period happens  when we are in our non REM 3 sleep. When we have sleep deprivation ( insomnia ), the heart have to keep pumping and working like normal. That gives rise to cardiac stress.  As evidenced by elevated levels of  all the cardiac stress hormones and inflammatory markers.

We now know that people who sleeps less than 6 hours a day have an increased incidence of heart disease, hypertension and diabetes mellitus. What is paradoxical is that there are some clinical studies which showed that those who sleep too long , also have an increase incidence of heart problems. Looks like 7-8 hours of sleep daily, is ideal.

A 2011 European Heart Journal review of 15 medical studies ( meta-analysis ) involving almost 475,000 people found that short sleepers had a 48% increased risk of developing or dying from coronary heart disease (CHD) in a seven to 25-year follow-up period (depending on the study) and a 15% greater risk of developing or dying from stroke during this same time. Interestingly, long sleepers -- those who averaged nine or more hours a night -- also showed a 38% increased risk of developing or dying from CHD and a 65% increased risk of stroke.

The association of hypertension and sleep deprivation is also rather strong. So also the association of sleep deprivation with insulin resistance and diabetes.

The issue of sleep deprivation and hypertension was well  written up in the 30^Th August 2011 issue of Time magazine and New York Times, Health column. Both articles highlighted the fact that lack of sleep is associated with a higher incidence of hypertension. I believe that this fact is well established.

The Sleep Heart Study ( Arch Int Med 2005 ),  was a large, cross-sectional, community-based study of the cardiovascular consequences of sleep disorder.   The authors assessed the relationship between reported sleep duration and impaired glucose tolerance or type 2 diabetes in more than 1,400 men and women who had no history of insomnia. After adjustment for age, sex, race, body habitus, and apnea-hypopnea index, the prevalence of impaired glucose tolerance and type 2 diabetes was higher in those who reported sleeping 6 hours or less per night—or 9 hours or more per night. This was reported in the medical journal. I believe that both these effects on hypertension and also diabetes are due to the excessive release of stress hormones and inflammatory markers in people who are sleep deprived.

SLEEP APNEA.

This is a sleep disorder characterised by cyclical noisy breathing followed by cessation of respiration. These cyclical breathing / apnea cycle may occur 10-30 times an hour and so these patients have almost no non REM 3 sleep.  As a result next day, they are exhausted, falling  asleep at meetings and even at traffic lights while driving.

These patients have associated increase risk of hypertension, diabetes, heart disease and strokes.

This condition can be remedied if the patient will consult with a neurologist.

Conclusion.

I have tried in this short article to give an overview of the importance of good sleep and the effect of bad sleep on the body as a whole and the heart and cardiovascular system in particular.

If I it all sounds a bit confusing or  far  fetched, at least remember that a good nght’s sleep is the foundation to a good heart and good health.