2Center for Demographic Studies, Duke University, Durham, USA

People at old ages suffer many chronic diseases and health impairments which means that the concept of 'cause specific mortality' could be misleading. Often at old ages a person dies not from a single cause but in the result of action of several causes and health conditions. These causes and conditions are mutually dependent and demand in specific analysis exists. The present report describes the time and age trends in structure of mortality in the presence of different conditions which are addressed as co-morbidity.

Public use data on Multiple Cause-of- Death for 1968-1999 provided by the National Center for Health Statistics USA were investigated. The data include all deaths occurring within the United States. Data are obtained from death certificates and include underlying cause of death and addition multiple conditions codes. The data are analyzed using tabulation by time and age for proportions of cause-specific deaths among all deaths under specified conditions. The results are visualized in form of color contour maps in time and age coordinates.

Trends in the mortality structure are clearly identified in the contour maps by age and by time. The role of co-morbidity increases with age. Some conditions demonstrate negative association with specific underlying cause of death. The example is total cancer as underlying cause of death and presence of asthma as condition. The proportion of death on cancer with asthma conditions up to three times lower than that without asthma.

Presented analysis indicates the influence of co-morbidity on mortality structure at old ages. Such relationships are to be incorporated in projection of trends in mortality and in estimation of health support programs efficiency. A protective role of some health conditions against death can reveal the new biological mechanisms for health protection.