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The effect of survival bias on case-control genetic association studies of highly lethal diseases.

ABSTRACT: BACKGROUND:Survival bias is the phenomenon by which individuals are excluded from analysis of a trait because of mortality related to the expression of that trait. In genetic association studies, variants increasing risk for disease onset as well as risk of disease-related mortality (lethality) could be difficult to detect in genetic association case-control designs, possibly leading to underestimation of a variant's effect on disease risk. METHODS AND RESULTS:We modeled cohorts for 3 diseases of high lethality (intracerebral hemorrhage, ischemic stroke, and myocardial infarction) using existing longitudinal data. Based on these models, we simulated case-control genetic association studies for genetic risk factors of varying effect sizes, lethality, and minor allele frequencies. For each disease, erosion of detected effect size was larger for case-control studies of individuals of advanced age (age >75 years) and/or variants with very high event-associated lethality (genotype relative risk for event-related death >2.0). We found that survival bias results in no more than 20% effect size erosion for cohorts with mean age <75 years, even for variants that double lethality risk. Furthermore, we found that increasing effect size erosion was accompanied by depletion of minor allele frequencies in the case population, yielding a "signature" of the presence of survival bias. CONCLUSIONS:Our simulation provides formulas to allow estimation of effect size erosion given a variant's odds ratio of disease, odds ratio of lethality, and minor allele frequencies. These formulas will add precision to power calculation and replication efforts for case-control genetic studies. Our approach requires validation using prospective data.

SUBMITTER: Anderson CD

PROVIDER: S-EPMC3080449 | biostudies-literature | 2011 Apr

REPOSITORIES: biostudies-literature

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The effect of survival bias on case-control genetic association studies of highly lethal diseases.

Anderson Christopher D CD Nalls Michael A MA Biffi Alessandro A Rost Natalia S NS Greenberg Steven M SM Singleton Andrew B AB Meschia James F JF Rosand Jonathan J

Circulation. Cardiovascular genetics 20110203 2

<h4>Background</h4>Survival bias is the phenomenon by which individuals are excluded from analysis of a trait because of mortality related to the expression of that trait. In genetic association studies, variants increasing risk for disease onset as well as risk of disease-related mortality (lethality) could be difficult to detect in genetic association case-control designs, possibly leading to underestimation of a variant's effect on disease risk.<h4>Methods and results</h4>We modeled cohorts f ...[more]

PMID: 21292865

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Project description:BackgroundDespite the limited genetic heterogeneity of Spanish populations, substantial evidences support that historical African influences have not affected them uniformly. Accounting for such population differences might be essential to reduce spurious results in association studies of genetic factors with disease. Using ancestry informative markers (AIMs), we aimed to measure the African influences in Spanish populations and to explore whether these might introduce statistical bias in population-based association studies.Methodology/principal findingsWe genotyped 93 AIMs in Spanish (from the Canary Islands and the Iberian Peninsula) and Northwest Africans, and conducted population and individual-based clustering analyses along with reference data from the HapMap, HGDP-CEPH, and other sources. We found significant differences for the Northwest African influence among Spanish populations from as low as ? 5% in Spanish from the Iberian Peninsula to as much as ? 17% in Canary Islanders, whereas the sub-Saharan African influence was negligible. Strikingly, the Northwest African ancestry showed a wide inter-individual variation in Canary Islanders ranging from 0% to 96%, reflecting the violent way the Islands were conquered and colonized by the Spanish in the XV century. As a consequence, a comparison of allele frequencies between Spanish samples from the Iberian Peninsula and the Canary Islands evidenced an excess of markers with significant differences. However, the inflation of p-values for the differences was adequately controlled by correcting for genetic ancestry estimates derived from a reduced number of AIMs.Conclusions/significanceAlthough the African influences estimated might be biased due to marker ascertainment, these results confirm that Northwest African genetic footprints are recognizable nowadays in the Spanish populations, particularly in Canary Islanders, and that the uneven African influences existing in these populations might increase the risk for false positives in association studies. Adjusting for population stratification assessed with a few dozen AIMs would be sufficient to control this effect.

Dataset Information

The effect of survival bias on case-control genetic association studies of highly lethal diseases.

Publications

The effect of survival bias on case-control genetic association studies of highly lethal diseases.

Similar Datasets

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