Why We Still Need More Research on the Epidemiology of Huntington's Disease

to agree upon as partial explanations for the rise in prevalence. They are also compatible with the stated finding that there has been no change in HD incidence at least in the UK. Increased awareness complemented by the availability of genetic testing is also compatible with this argument provided that it does not lead to ascertainment of completely new cases that otherwise would not have been diagnosed except to persons at risk being diagnosed earlier and thus live longer with diagnosed HD. Considering that the HTT mutation is not a disease in itself but an autosomal dominantly inherited trait and the subjective element inherent in contemporary diagnostic criteria of manifest HD, this is quite possible. On the other hand, incidence studies from other Caucasian populations seem to suggest an increasing trend [1, 3] and data concerning new mutation rates are incomplete. Furthermore, while we do not know the impact the introduction of genetic testing has had upon case ascertainment and diagnosis, it feels sensible to assume that making a diagnosis in uncertain and improbable cases has become easier and even more common. Many studies have indeed recently noted that a considerable number of new patients have no family history of HD and proportions of late-onset cases (at least 60 years of age at motor onset) have increased (for instance [4–6] ). This is also Nearly a quarter of a century ago, the mutation underlying Huntington’s disease (HD), a dynamic cytosine-adenine-guanine (CAG) repeat expansion of the Huntingtin (HTT) gene located in chromosome 4, was discovered. We have learned much since then, but more work remains if we are to find a cure for this disease. Perhaps, surprisingly, 144 years after George Huntington gave his speech on chorea, this is also true concerning HD epidemiology. Like earlier studies, a recent review found HD prevalence to be highest in populations of Caucasian descent at 5.7 per 100,000 [1] . However, a rise has been postulated and both estimates in the traditional prevalence range, but considerably higher figures have also been published recently. In their paper, in this issue of Neuroepidemiology , Rawlins et al. [2] review all prevalence studies published to date and provide a meta-analysis confirming a trend of increasing HD prevalence in most populations of Caucasian descent. While their results also confirm that the disease is most prevalent in Caucasian populations, they also point out that more studies of HD epidemiology are needed, not only in South America and Africa but also in Asia and even Central and Eastern Europe. Increase in population longevity and possibly longer survival of HD patients due to better treatment are easy Published online: February 3, 2016