Population Genetics
Part 7

An examination of the origin and frequency of HD

How does HD affect fertility and reproductive fitness?

Currently, there are conflicting findings on the effect of HD on one’s fertility and reproductive fitness. Many studies have found that people with HD, compare to general population, have an increased fertility and fitness before they develop symptoms. Most notably, studies in Canada, Minnesota, England, Wales, and Tasmania have found an increased fertility and reproductive fitness in presymptomatic persons with HD. However, some studies, like one performed in Queensland, Australia, found an identical fertility and fitness among persons with HD and the general population. In addition, other studies carried out in Michigan and Japan found decreased fertility and fitness among persons with HD.

In general, most studies find an increase in fertility and reproductive fitness among presymptomatic people with HD. It has been hypothesized that some early features of HD – possibly increased sexual drive, loss of impulse control, and impaired cognition and judgment – may be responsible for this increased reproduction. At this time, however, there is no published evidence to support these possible mechanisms for increased fertility. The hypothesis of increased fertility and reproduction among presymptomatic individuals remains speculative.

One study in Tasmania, Australia found that the increased fertility was especially prevalent in people with late-onset HD. People with early-onset HD did not exhibit a similar increase. Logically, if people start to develop HD symptoms before they complete their families, the early symptoms of HD could well decrease their chances of pregnancy and children. Such an effect has been found in the case of juvenile HD, in which HD symptoms develop in childhood or adolescence and significantly reduce a person’s reproductive ability. (To learn more about Juvenile HD, click here.) Given enough time to complete their families, though, it seems that presymptomatic people with HD could well have, on average, more children than people without HD. Keep in mind, however, that there is contradictory evidence from some locations and that none of the hypothetical mechanisms have been confirmed.

Last Modified: 04/12/2007

An educational product of HOPES, not to be used in place of medical care. For more information about HOPES, click on the Logo. To contact HOPES with comments or questions, click here.