Sleeping well involves 7 to 9 hours of good night's sleep. Poor sleep quality is a serious risk factor that affects health in general and cardiac function in particular.
The heart beats at an average of 70 beats per minute, 100,000 times per day, 35 million per year and a little more than 2.5 billion in the life of a person of about 80 years of age on average. The correct equation (nighttime predominance of the parasympathetic over the sympathetic) when sleeping well allows blood pressure and heart rate to drop.