The team investigated whether genetic anticipation occurs in Crohn's disease or not.
They reported their findings in the latest issue of the Annals of Internal Medicine.
Genetic anticipation is when genetically-transmitted disease manifests at increasingly younger ages, with each succeeding generation. Some researchers have claimed that this phenomenon is observed in polygenic disorders, such as Crohn's, in which its mechanism cannot be explained.
The investigators compared the ages at diagnosis of Crohn's disease, among different birth cohorts, before and after adjustment for observation time. A total of 928 consecutive Crohn's outpatients were included in the study.
Trends in age at diagnosis of Crohn's disease, among birth cohorts, were determined by calculating Pearson correlation coefficients and performing Kaplan-Meyer analysis. This was done before and after adjustment for observation time.
|Genetic anticipation is when genetically-transmitted disease manifests at increasingly younger ages, with each succeeding generation.
|Annals of Internal Medicine|
The researchers ensured that the time all included patients were at risk of Crohn's disease was equal. They also adjusted for observation time by ensuring that all patients had developed the disease by the end of the risk period.
It was found that mean age at diagnosis decreased by approximately 5 years, with each subsequent 10-year birth cohort. This was on the basis of crude cross-sectional data, and could suggest genetic anticipation between generations.
However, after adjustment for observation time, the age at diagnosis decreased minimally, if at all, with each successive generation.
Dr Michael F. Picco, of the Mayo Clinic, Jacksonville, Florida, said on behalf of his colleagues, "Apparent genetic anticipation can be explained by observational biases, without invoking any additional genetic influences."
"Claims for genetic anticipation must be based on methods that properly account for the duration of observation in all persons being studied," he concluded.