Hepatitis C virus infection mortality trends according to three definitions with special concern for the baby boomer birth cohort.

We examined mortality trends of hepatitis C virus (HCV) infection in the United States in 1999-2018 according to the following definitions: HCV as the underlying cause of death (UCOD), HCV mentioned anywhere on the death certificate (mentioned), and HCV recorded in Part 1 of the death certificate. By using entity axis information in mortality multiple-cause files, we ascertained the position of HCV on the death certificate. Joinpoint regression analysis was used to evaluate changes in HCV mortality rates according to the definitions. The age-standardized HCV mortality rates (deaths per 100,000 people) in terms of UCOD, mentioned, and Part 1 were, respectively, 1.36, 2.87 and 1.94, in 1999; increased to 1.90, 5.09 and 2.96 in 2013; and declined to 0.98, 3.77 and 2.29 in 2018. The mentioned/UCOD mortality ratio was 2.11 in 1999 and increased to 3.86 in 2018. The mentioned/Part 1 ratio was almost identical (ie 1.48 in 1999 and 1.65 in 2018). The extent of decline from 2014 to 2018 differed according to the definitions; the annual per cent changes for UCOD, mentioned, and Part 1 were -14.6%, -7.1% and -9.8%, respectively. For the same age group, the baby boomer subcohort 1950-1954 had the highest mortality rates among the subcohorts (1945-1949, 1955-1959 and 1960-1964). HCV mortality according to HCV in Part 1 of the death certificate-the explicit opinion of a certifying physician that HCV played a substantial role and directly caused death-differed from that according to HCV as UCOD and HCV mentioned.