Why most deaths occur at morning hours 6 a.m. to 9 a.m. ?

 Human mortality rises rapidly from a low at 12 a.m. to 2 a.m. to a peak at 6 a.m. to 9 a.m., according to reported times of death from death certificates . This is because of following reason

1) Circadian rhythms / Biological clock Induced sympathetic surge :-

While you are sleeping your heart rate falls and your blood pressure falls ( heart rate and blood pressure falls in sleep because you aren’t doing any work so you don’t need much oxygen and glucose , so your heart need not pump much blood , so your heart rate decreases at night) . But at morning 6 a.m.  to 9 a.m. there will be abrupt rise in your heart rate and blood pressure due to endogenous circadian peak / Increase in Plasma Cortisol and Plasma Epinephrine and Largest circadian decrease in cardiac vagal modulation especially at around 9.00 a.m. ( Sympathetic nervous system stimulation / Sympathetic surge ) because everyone almost wakes up from sleep at this time and goes to work , so you require more oxygen and glucose during work , so heart must pump more blood so heart rate increases.

1. In people with heart diseases (Coronary artery disease / Ischemic Heart Disease) the heart cannot tolerate these sudden changes in Heart rate and Blood pressure and at last the heart gives up and people die of Heart attacks .( So peak deaths occur at 6.00 a.m. to 9.00 a.m.) 

2. Also increased death rates are seen at 12.00 a.m. to 2.00 a.m. because the symptoms of sudden cardiac arrest / Stroke may go unnoticed because you are sleeping . 

2)  Circadian rhythms / Biological clock Induced Blood clotting :-

Human circadian system causes morning peak  in circulating levels of PAI-1 (Plasminogen activator inhibitor-1 ) at almost 6.30 a.m. , which prevents blood clot breaking down / fibrinolysis. This increases chances of heart attack and stroke.

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