Death is the permanent end of the life of a biological organism. Death may refer to the end of life as either an event or condition. Many factors can cause or contribute to an organism's death, including predation, disease, habitat destruction, senescence, malnutrition and accidents. The principal causes of death in developed countries are diseases related to aging. Traditions and beliefs related to death are an important part of human culture, and central to many religions. In medicine, biological details and definitions of death have become increasingly complicated as technology advances.
Death can be caused by disease, accident, homicide, or suicide. The leading cause of death in developing countries is infectious disease. The leading causes of death in developed countries are atherosclerosis (heart disease and stroke), cancer, and other diseases related to obesity and aging. These conditions cause loss of homeostasis, leading to cardiac arrest, causing loss of oxygen and nutrient supply, causing irreversible deterioration of the brain and other tissues. With improved medical capability, dying has become a condition to be managed. Home deaths, once the norm, are now rare in the first world.
In developing nations, inferior sanitary conditions and lack of access to medical technology makes death from infectious diseases more common than in developed countries. One such disease is tuberculosis, a bacterial disease which killed 1.7 million people in 2004.
Many leading first world causes of death can be postponed by diet and physical activity, but the accelerating incidence of disease with age still imposes limits on human longevity. The evolutionary cause of aging is, at best, only just beginning to be understood. It has been suggested that direct intervention in the aging process may now be the most effective intervention against major causes of death.