Are incidence rates of adult leukemia in the United States significantly associated with birth cohort?

BACKGROUND

Leukemia is a common cancer among U.S. adults but there are few established risk factors. If leukemia risks are substantially influenced by exposures that vary in prevalence across generations, then population incidence rates should vary significantly by birth cohort. However, prior studies have not examined leukemia birth cohort effects using contemporary data and methods.

METHODS

We used incidence data from the National Cancer Institute's Surveillance, Epidemiology and End Results Program from 1992 through 2009 for adults 25-84 years old and age period cohort models to estimate incidence rate ratios according to birth cohort for acute myeloid leukemia (AML), acute lymphoid leukemia (ALL), chronic myeloid leukemia (CML), and chronic lymphoid leukemia (CLL).

RESULTS

Leukemia incidence varied significantly between birth cohorts for each major leukemia type in men and women except female AMLs; changes on the order of 1% per birth year or 20% per generation were observed. The most significant birth cohort signatures were observed for CLLs and AMLs in men, which were decreasing and increasing, respectively, in cohorts born since 1946.

CONCLUSIONS

Our results support the hypothesis that adult leukemia risks are significantly modulated by environmental and lifestyle exposures.

IMPACT

A number of well-established (smoking, certain chemicals, radiation) and newly recognized (obesity) leukemia risk factors are modifiable; ultimately, efforts to promote healthy lifestyles might also help reduce incidence rates of adult leukemia.