Objective To assess reporting change for unintentional injury mortality data for Americans aged 65+from 1999 to 2016 and quantify its contribution to reported underlying cause of death (UCD)-based mortality.

Methods Using data from the US. Center for Disease Control and Prevention WONDER online databases, we developed a simple model to estimate injury mortality attributed to data reporting changes in cause specificity and selection of UCD from multiple cause of death (MCD) during 1999–2016.

Findings From 1999 through 2016, the proportion of MCD-based cause-specific unintentional injury mortality increased from 74% to 85%; proportions of UCD/MCD mortality for overall and cause-specific unintentional injury rose substantially in all specific causes except motor vehicle crashes. Age-adjusted UCD-based mortality attributed to data reporting changes increased gradually and distinctly between 1999 and 2016; the increase for overall unintentional injury, falls, motor vehicle crashes, suffocation, poisoning, and fire/burn was 24.2, 13.5, 2.1, 2.3, 1.6 and 0.4 per 1 00 000 persons, respectively. Percent change in mortality between 1999 and 2016 differed greatly between reported and adjusted UCD-based mortality – overall unintentional injury, 18% vs −10%; falls, 113% vs 63%; motor vehicle crashes, −35% vs −44%; suffocation, −18% vs −48%; poisoning, 134% vs 64%; fire/burn, −32% vs −42%.

Conclusion Data reporting changes have affected reported UCD-based overall and cause-specific unintentional injury mortality for older Americans and altered their trends from 1999 to 2016. Data reporting changes should be considered in interpreting change in overall and specific unintentional injury mortality over time for older Americans.