Counting injury deaths: Underlying vs. multiple causes of death mortality data

Background/Purpose: Estimation of number of injury deaths might be different according to different definitions. This study aimed to compare the number of injury deaths estimated according to underlying (U) with multiple (M) cause-of-death (COD) mortality data in the United States. Methods: The Multiple-Cause Mortality Files compiled by the National Center for Health Statistics for year 2009 were used to calculate the U/M ratio by different external causes of injury. Results/Outcomes: There were 117,006 unintentional injury deaths according to underlying COD and 149,144 deaths according to multiple COD with a U/M ratio of 78.5%. The U/M ratio was high for deaths from transport injuries (98.4%), exposure to inanimate mechanical forces (96.0%), unintentional drowning and submersion (96.3%), exposure to smoke, fire and flames (95.4%), intentional self-harm (99.7%), and assault (98.6%). On the contrary, the U/M ratio was low for deaths from threats to breathing (28.3%), exposure to forces of nature (60.2%), and complications of medical and surgical care (10.1%). Conclusions: Number of injury deaths estimated according to underlying COD differed greatly with those according to multiple COD in some external causes of injury, such as choking/suffocation and complications of medical and surgical care. To better estimate the number of injury deaths, both underlying and multiple COD mortality data should be used.