In law, medicine, and statistics, cause of death is a term which refers to an official determination of conditions resulting in a human's death. In modern times, such determinations usually become an essential data point of an official death certificate.
In contemporary times and in most parts of the world, a cause of death is determined by a medical examiner.
A study published in Preventing Chronic Disease found that only one-third of New York City resident physicians reported believing that the present system of documentation was accurate. Half reported the inability to record "what they felt to be the correct cause of death", citing reasons such as technical limitation and instruction to "put something else". Nearly four-fifths reported being unaware that determinations of "probable", "presumed", or "undetermined" could be made, fewer than three percent reported ever updating a death certificate when conflicting lab results or other new information became available, and cardiovascular disease was indicated as "the most frequent diagnosis inaccurately reported".
Causes of death are sometimes disputed by relatives or members of the public, particularly when some degree of uncertainty or ambiguity exists in relation to the cause of death. On occasion, such disputes may result from, or sometimes instigate, a conspiracy theory.
"Old age" in of itself is not a direct cause of death; the direct cause can always in theory be attributed to a specific disease or failed organ system. However, over time, in most (but not all) organisms, many critical biological systems experience chemical or physical damage which eventually accumulate enough to cause failure. This is a significant problem in humans; it is estimated that of the roughly 150,000 people who die each day across the globe, about two thirds—100,000 per day—die of age-related causes. In industrialized nations the proportion is much higher, reaching 90%. Thus as an indirect cause, biological aging is by far the leading cause of death.
An alternative view of mortality is to consider the estimated loss in life-years from causes of death other than age-related. An infographic prepared by Thomas Porostocky and published in 2013 compares 2005 to 2010 in this "life-years lost annually" dimension.
There are also popular notions that someone can be "scared to death" or die of loneliness or heartbreak. Death caused by fear or stress can indeed have direct physiological effects. For example, it has been proposed that overstimulation of the Vagus nerve - which suppresses heart rate in a mechanism related to the behavior of apparent death or "playing possum" - is the cause of documented cases of psychogenic death. The flight or fight response to fear or stress has the opposite effect, increasing heart rate through stress hormones, and can cause cardiovascular problems (especially in those with pre-existing conditions). This is the proposed mechanism for the observed increase in the death rate due to cardiac arrest after widely experienced acutely stressful events such as terrorism, military attacks, and natural disasters (even among those who are not in the affected area) and for documented deaths in muggings and other frightening events which caused no traumatic physical harm. The proximal medical cause of death in these cases is likely to be recorded as cardiac failure or vagal inhibition (which also has other potential causes such as blows to certain parts of the body and nerve injuries).
One specific condition observed to result from acute stress, takotsubo cardiomyopathy, is nicknamed "broken heart syndrome", but the stress need not be relationship-related and need not be negative.
Some insurance contracts, such as life insurance policies, have special rules for certain causes of death. Intentional injuries, for example, may invalidate claims under terms of such a contract.