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

<b><i>Objective:</i></b> To estimate the statistical distribution of the incubation period of Creutzfeldt–Jakob disease (CJD) in human growth hormone (hGH) recipients in France. <b><i>Background:</i></b> Published papers suggest that the median incubation period of hGH-related CJD is approximately 15 years, but there are as yet no statistical data that support this assertion. <b><i>Methods:</i></b> Of the 1,361 hGH recipients who were included in this study, 55 had developed CJD at the time of the study. Individual data on hGH treatment history were available. Different mathematical models were used to estimate the statistical distribution of the incubation period. One main feature of the models was to take into account the occurrence of future CJD cases. <b><i>Results:</i></b> Models showed that 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 incubation period was significantly shorter in homozygotes at codon 129 of the prion protein gene than in heterozygotes. <b><i>Conclusions:</i></b> The short mean incubation period of CJD in French hGH recipients may be due to high infectivity in hormone lots. Estimates of the 95th percentile indicate that the number of hGH-related CJD cases may continue to increase in the coming years.