Linking Cancer and Dementia: The Importance of considering the Competing Risk of Mortality

Heidi A. Hanson, University of Utah
Ken R. Smith, University of Utah
Kevin Horn, University of Utah
Kelli Rasmussen, University of Utah
Site Li, University of Utah
John Hoffman, University of Utah

Cancer survivors in the United States number 14 million (2012) with 60% at ages 65+. At the same time, there are 40 million persons living with some form of dementia. This study examines the link between these two profoundly important diseases. We use the Utah Population Database (UPDB), a representative and very-large population-based resource of linked medical and genealogical records, to test the hypothesis that cancer survivors have an elevated risk of dementia when controlling for the competing risk of mortality. The UPDB gives us the unique capability of using data on sets of relatives to control for unobserved heterogeneity and introduce measures of familial risks of cancer as a moderator; this type of analysis is not possible anywhere in the United States. We find that failure to account for the competing risk of mortality can lead to erroneous conclusions about the relationship between cancer and later life dementia.