Incubation period of Creutzfeldt-Jakob disease in human growth hormone recipients in France

Objective: To estimate the statistical distribution of the incubation perio d of Creutzfeldt-Jakob disease (CJD) in human growth hormone (hGH) recipien ts in France. Background: Published papers suggest that the median incubati on period of hGH-related CJD is approximately 15 years, but there are as ye t no statistical data that support this assertion. Methods: Of the 1,361 hG H recipients who were included in this study, 55 had developed CJD at the t ime of the study. Individual data on hGH treatment history were available. Different mathematical models were used to estimate the statistical distrib ution of the incubation period. One main feature of the models was to take into account the occurrence of future CJD cases. Results: Models showed tha t the mean incubation period was 9 to 10 years, and the 95th percentile of the distribution was 15 to 16 years. Data and models indicated that the inc ubation period was significantly shorter in homozygotes at codon 129 of the prion protein gene than in heterozygotes, Conclusions: The short mean incu bation period of CJD in French hGH recipients may be due to high infectivit y in hormone lots. Estimates of the 95th percentile indicate that the numbe r of hGH-related CJD cases may continue to increase in the coming years.