Incidence Statistics
How common is Angelman Syndrome?
The answer to this question is not precisely known but we do have some estimates. The best available data come from studies of school age children, ages 6-13 years, living in Sweden, and from Denmark where the diagnosis of AS children in medical clinics was compared to an 8 year period of about 45,000 births. The Swedish study showed an AS prevalence of about 1/12,000 (Steffenburg et al., 1996) and the Danish study showed a minimum AS prevalence of about 1/10,000 (Petersen et al., 1995). Note that it is desirable to use the term prevalence since estimates of the AS diagnosis have been made in relatively small cohorts of children over various periods of time.
Several reports have tried to address the prevalence of AS among groups of individuals with established developmental delay. The results showed rates of 0% (Vercesi et al., 1999), 1.3% (Aquino et al., 2002), 1.4% (Jacobsen et al., 1998), and 4.8% (Buckley et al., 1998). The Buckley paper extrapolated their data in order to compare it to the population of the state of Washington (using 1997 Census Bureau figures) and obtained an estimate of 1/20,000, a number similar to that often quoted, but not referenced in terms of methodology, in a 1992 review paper (Clayton-Smith and Pembrey 1992).
There appear to be no reported prevalence studies that have screened newborns to detect rates of AS. Population wide prevalence figures would need to take into consideration that longevity in AS is probably reduced (severe mental delay and seizure presence would be risk factors) but no actuarial or other data are available on life span shortening. Likewise, it is not known what percent of individuals with AS are undiagnosed, although this is expected it to be significant. Accordingly, to estimate the number of people with AS living in the society, it would be inaccurate to divide any estimated AS prevalence figure into a total population number.
Given this information, it appears that the prevalence of AS among children and young adults is between 1/10,000 and 1/20,000. It is suggested to use a 1/15,000 figure if a single figure is needed. For population projections, estimates using birth rates can be used. For example, if an area has a birth rate of about 200,000/year it would be estimated that about 13 babies would be born each year with AS.
Charles Williams, MD
January 30, 2003
Reviewed 6-25-05
Reviewed 11-4-08
References:
Aquino NH, Bastos E, Fonseca LC, Llerena JC, Jr. 2002. Angelman syndrome methylation screening of 15q11-q13 in institutionalized individuals with severe mental retardation. Genet Test 6(2):129-31.
Buckley RH, Dinno N, Weber P. 1998. Angelman syndrome: are the estimates too low? Am J Med Genet 80(4):385-90.
Clayton-Smith J, Pembrey ME. 1992. Angelman syndrome. J Med Genet 29(6):412-5.
Jacobsen J, King BH, Leventhal BL, Christian SL, Ledbetter DH, Cook EH, Jr. 1998. Molecular screening for proximal 15q abnormalities in a mentally retarded population. J Med Genet 35(7):534-8.
Petersen MB, Brondum-Nielsen K, Hansen LK, Wulff K. 1995. Clinical, cytogenetic, and molecular diagnosis of Angelman syndrome: estimated prevalence rate in a Danish county. Am J Med Genet 60(3):261-2.
Steffenburg S, Gillberg CL, Steffenburg U, Kyllerman M. 1996. Autism in Angelman syndrome: a population-based study. Pediatr Neurol 14(2):131-6.
Vercesi AM, Carvalho MR, Aguiar MJ, Pena SD. 1999. Prevalence of Prader-Willi and Angelman syndromes among mentally retarded boys in Brazil. J Med Genet 36(6):498.