Persons most commonly affected: Elderly people of both sexes.

Organ or part of body involved: Heart

Symptoms and indications: A heart rate below 55 beats per minute. Typical symptoms of bradycardia include fatigue, shortness of breath, dizziness and fainting (syncope).

Causes and risk factors: May occur either under nervous system control, as in the gag or diving reflexes that cause the heart to slow, or as a general sign of diminishing blood oxygen concentration, as seen with infantile apnea or in shock. It may also be due to post-myocardial infarction or the hypofunction of the thyroid gland.

Prevention: Drink plenty of water - eight to 10 glasses a day. Eat a heart-healthy diet and eliminate unnecessary stress. Exercise regularly - especially aerobic activity like walking, cycling, jogging, or swimming and maintain a healthy weight. Don't smoke and linger where there is second-hand smoke - smoking is a leading cause of heart disease. Avoid drinking excessive amounts of alcohol, caffeine, or sugary drinks.