The decline in U.S. cancer mortality in people born since 1925

Abstract

The conventional practice of analyzing overall age-adjusted cancer mortality rates heavily emphasizes the experience of older, higher mortality age groups. This may conceal shifts in lifetime cancer mortality experience emerging first in younger age groups. We examined age-specific cancer mortality rates and birth cohort-specific cancer mortality rates in U.S. mortality data recorded since 1955 to assess the effects of age, period, and cohort in secular mortality trends. Cancer mortality and population data were obtained from WHO Statistical Information System. Age-specific cancer mortality rates have been steadily declining in the United States since the early 1950s, beginning with children and young adults and now including all age groups. During the second half of the 20th century, each successive decade of births from 1925 to 1995 experienced a lower risk of cancer death than its predecessor at virtually every age for which such a comparison can be made. A major decline in cancer mortality has been occurring in the United States for the past 50 years, affecting birth cohorts born as long as 80 years ago. Excepting lung cancer, much of this decline has occurred despite relatively stable cancer incidence. These findings suggest that improvements in cancer detection, treatment, and/or prevention have reduced the risk of cancer death across the life span for individuals born in the last three quarters of the 20th century.

Figure 1

All-site cancer mortality rates at different ages by decade of birth. Mortality rates for 40-79 year olds are plotted stratified by age and plotted by year of birth.

Figure 2

All-site cancer rates in successive birth cohorts by age of death. Mortality rates for decadal birth cohorts between 1925 and 2004 are plotted by age at death.

Figure 3

Bayesian age, period, and birth-cohort analysis of all-site cancer mortality data. The contributions of (A) age, (B) period and (C) birth-cohort to cancer mortality risk are plotted. Rate ratio refers to the ratio of the mortality rate at the specified interval compared to the average over the entire range plotted. The dotted red line indicates the 95% credible bounds of the estimate.

Figure 4

Annual percent change in age-adjusted mortality rate (red line) and unweighted average mortality rate across all age groups from 20 to 85+ years of age (gray line).