Relative risks of diseases in the presence of incomplete penetrance and sporadics

Partha P. Majumder, Ranajit Chakraborty, Kenneth M. Weiss

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


In most diseases of contemporary interest to epidemiology, the importance of familial risk factors is often assessed by relative risk measures computed from family history data. In this paper, we examine the efficiency of relative risk measures in discerning the genetic background of a disease. It is shown that even for a simple (one locus, two alleles) genetic disease, incomplete penetrance of the disease allele and/or occurrence of sporadics (i.e. non‐heritable cases caused by environmental risk factors) often yields a rather small value of relative risk. This means that a small value of relative risk need not necessarily imply that genetic factors are unimportant in the aetiology of the disease. Furthermore, it is shown that the relative risk measures are complicated functions of disease gene frequency, the penetrance parameter and the sporadic rate. A rejection of genetic involvement for a disease on the basis of a single relative risk estimate may, therefore, be erroneous.

Original languageEnglish
Pages (from-to)13-24
Number of pages12
JournalStatistics in Medicine
Issue number1
StatePublished - 1983


  • Genetic epidemiology
  • Incomplete penetrance
  • Relative risk
  • Sporadics


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