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Huntington Disease (HD)

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Epidemiology

Huntington disease (HD) is a progressive, neurodegenerative, genetic disorder characterized by involuntary, unpredictable, sudden movements (chorea) of the extremities and facial muscles, as well as cognitive decline and emotional disturbances.1,2 

Incidence and Prevalence of HD

In 2012, researchers conducted a systematic review and meta-analysis of the literature published between 1985 and 2010, reporting that the pooled global incidence of HD according to 4 incidence studies was around 0.38 cases per 100,000 person-years.3 They estimated that the global prevalence of HD was around 2.7 per 100,000 persons.1,3 

In 2022, researchers published an updated systematic review and meta-analysis of the literature published between 2010 and February 2022. They pooled data from 13 of 18 available incidence studies and 23 of 27 available prevalence studies for the meta-analysis. The pooled global incidence of HD rose to 0.48 cases per 100,000 person-years, and the pooled global prevalence of HD rose to 4.88 per 100,000 persons.4 

The authors attributed the rise in HD incidence and prevalence over the past decade to advancements in molecular genetic testing, earlier diagnosis, increased life expectancy among those with HD, and de novo mutations (which accounted for up to 7.1% of cases). Additionally, more epidemiological studies were published between 2010 and 2022 than from 1985 to 2010.4

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Race, Ethnicity, and Geographic Factors of HD

Although HD affects individuals of every race and ethnicity,5 its prevalence is consistently higher among individuals with European ancestry living in Europe, North America, and Australia than in individuals living in Asia and Africa.1,2,4,5 HD prevalence ranges from 3 to 7 per 100,000 persons among those with European ancestry.2

The prevalence of HD is estimated at 6.37 per 100,000 persons in Europe and 8.87 per 100,000 persons in North America. In stark contrast, HD prevalence is estimated at around 0.25 per 100,000 persons in Africa, 0.41 per 100,000 persons in East Asia, and 2.39 per 100,000 persons in calculations combining both the Middle East and East Asia. Countries in the Middle East (Israel and Oman) each demonstrated a prevalence (4.36 and 7.36 per 100,000 persons, respectively) that was similar to that in Europe and North America.4

One geographical region in Ervalia, a town in Brazil, was found to have a cluster of people affected by HD, with a prevalence at least 10 times higher than that reported in other studies in South America, North America, and Europe.6 Researchers calculated the HD prevalence in this geographic cluster to be around 7.2 per 10,000 persons6 or 71.87 per 100,000 persons.4

Different HTT gene haplotypes, de novo mutation rates, health care accessibility, and illness-related stigmas may account for this ethnic variation and the higher prevalence among individuals of European ancestry.1,4,5

Read more about HD genetics

Sex Factors of HD

HD affects both biological sexes equally, as it is a nonsex-linked disorder with an autosomal dominant pattern of inheritance.7 Although men and women have an equal risk of inheriting HD,8 studies indicate that women experience more severe symptoms of HD than men, especially those related to depression. Motor and cognitive decline are also more significant in women than in men, suggesting that sex differences affect disease progression.9,10 

Read more about HD prognosis

Age Factors of HD

The most common subtype of HD is the adult-onset type.2 Adult-onset HD typically manifests between the ages of 30 and 50 years.2,11 Symptoms of the juvenile subtype of HD appear during childhood or adolescence.2 Any individual with an onset of HD symptoms prior to the age of 21 years is diagnosed with juvenile HD. Juvenile HD accounts for 4% to 10% of all HD cases.12

Age of disease onset is inversely related to the length of CAG repeats in the causative HTT gene, which accounts for around 60% of the variance in initial symptom onset.5,11 Patients with late-onset HD, which manifests at 60 years of age or over, demonstrate an average CAG repeat length of 40.9.11,13

Read more about HD pathophysiology

References

  1. Ajitkumar A, De Jesus O. Huntington disease. In: StatPearls [Internet]. Treasure Island, FL: StatPearls Publishing; 2023. Updated February 12, 2023. Accessed August 5, 2023.
  2. Huntington disease. MedlinePlus. Updated July 1, 2020. Accessed August 5, 2023.
  3. Pringsheim T, Wiltshire K, Day L, Dykeman J, Steeves T, Jette N. The incidence and prevalence of Huntington’s disease: a systematic review and meta-analysis. Mov Disord. 2012;27(9):1083-1091. doi:10.1002/mds.25075
  4. Medina A, Mahjoub Y, Shaver L, Pringsheim T. Prevalence and incidence of Huntington’s disease: an updated systematic review and meta-analysis. Mov Disord. 2022;37(12):2327-2335. doi:10.1002/mds.29228
  5. Kay C, Hayden MR, Leavitt BR. Epidemiology of Huntington disease. In: Feigin AS, Anderson KE, eds. Handbook of Clinical Neurology. Vol 144. Elsevier; 2017:31-46. doi:10.1016/B978-0-12-801893-4.00003-1
  6. Agostinho LDA, da Silva IDS, Maia LA, et al. A study of a geographical cluster of Huntington’s disease in a Brazilian town of Zona da Mata, Minas Gerais State. Eur Neurol. 2015;74(1-2):62-68. doi:10.1159/000434630
  7. Gonzalez-Usigli HA. Huntington disease. Merck Manual Professional Version. Updated September 2022. Accessed August 5, 2023. 
  8. What is Huntington disease? Huntington Society of Canada. Accessed August 5, 2023.
  9. Hentosh S, Zhu L, Patino J, Furr JW, Rocha NP, Furr-Stimming E. Sex differences in Huntington’s disease: evaluating the Enroll-HD database. Mov Disord Clin Pract. 2021;8(3):420-426. doi:10.1002/mdc3.13178
  10. Kuljis DA, Gad L, Loh DH, et al. Sex differences in circadian dysfunction in the BACHD mouse model of Huntington’s disease. PLoS One. 2016;11(2):e0147583. doi:10.1371/journal.pone.0147583
  11. Anil M, Mason SL, Barker RA. The clinical features and progression of late-onset versus younger-onset in an adult cohort of Huntington’s disease patients. J Huntingtons Dis. 2020;9(3):275-282. doi:10.3233/JHD-200404
  12. Bakels HS, Roos RAC, van Roon-Mom WMC, de Bot ST. Juvenile-onset Huntington disease pathophysiology and neurodevelopment: a review. Mov Disord. 2022;37(1):16-24. doi:10.1002/mds.28823
  13. Chaganti SS, McCusker EA, Loy CT. What do we know about late onset Huntington’s disease? J Huntingtons Dis. 2017;6(2):95-103. doi:10.3233/JHD-170247

Reviewed by Hasan Avcu, MD, on 8/9/2023.

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