When people die. Cause of death versus time of death.

A sample of 4,920 disease-related deaths from New York City for 1979 (8.7 percent of all relevant data from New York City's files) showed a 60 percent rise in death rate beginning at 2 A.M. and reaching a peak at 8 A.M. A smaller peak was also noted at 6 P.M. The rise in human mortality beginning at 2 A.M. and peaking at 8 A.M. might be explained by: artifact of deaths occurring anytime during the night that are discovered after daybreak, effect of less efficient health care between 2 A.M. and 8 A.M., and disease processes that somehow increase risk of death between 2 A.M. and 8 A.M. An attempt was made to differentiate among these possibilities by comparing time of death for various subsamples. The bimodal pattern appeared only in the temporal distribution of deaths of persons over 65 years of age; deaths of persons under 65 did not show significant temporal concentration. There were also prominent differences in the distribution of deaths for different reported causes of death. Ischemic heart disease, which numerically accounted for over 50 percent of the sample, showed peak mortality at 8 A.M. for both males and females. Hypertensive disease showed a significant peak in mortality at 1 A.M. for females only. Cerebrovascular disease peaked significantly at 6 A.M. with a significant peak only for males. The age and disease specificity of the 2 A.M. to 8 A.M. rise in death is consistent with a disease-related explanation for the bimodal circadian pattern in mortality. The quality and efficiency of health care could be improved with more precise information on peak periods of risk for specific morbid conditions.