Using the Population Attributable Fraction to Measure Heritability in Dichotomous Twin Data

• Activity Number: 183
• Type: Contributed
• Date/Time: Monday, July 30, 2012 : 10:30 AM to 12:20 PM
• Sponsor: Section on Statistics in Epidemiology
• Author(s): Leroy R Thacker*+ and Viswanathan Ramakrishnan
• Companies: Virginia Commonwealth University and Medical University of South Carolina
• Keywords: Dichotomous twin data ; Odds ratio ; Population attributable fraction

Abstract

In many genetic analyses of dichotomous cancer, twin-data odds ratios have been used to test hypotheses on heritability and shared common environment effects of a given disease (Lichtenstein et. al., 2000, Ahlbom et. al., 1997, Ramakrishnan, et. al., 1992, 1996). However, meaningful estimates for these two effects are not currently available in the literature. In epidemiology, the attributable fraction (AF), a function of the odds ratio and the prevalence of the risk factor, has been widely used to describe the contribution of a risk factor to a disease in a given population (Leviton, 1973). In our presentation we adapt the AF to quantify the heritability and the shared common environment in dichotomous cancer data. Cancer data from the Swedish Twin Registry (Lichtenstein, et. al., 2000; Katsika, et. al., 2005; Lichtenstein and Annas, 2000) are used to estimate the AF. The results show, for example, that 3.0% (+1.6%) of the breast cancers in women is attributable to inheritance while about 1.7% (+2.0%) of the breast cancers in women are attributable to shared common environment. A simulation study also was performed to study the variance characteristics of the estimate of the AF.