[1] According to Daphna Birenbaum Carmeli at the University of Haifa, Jewish populations have been studied thoroughly because:[10] The result is a form of ascertainment bias.
For example, a series of publications on Ashkenazi centenarians established their longevity was strongly inherited and associated with lower rates of age-related diseases.
[12] Because of centuries of endogamy, today's 10 million Ashkenazi Jews descend from a population of 350 who lived about 600–800 years ago.
[5] Tay–Sachs disease, which can present as a fatal illness of children that causes mental deterioration prior to death, was historically extremely common among Ashkenazi Jews,[19] with lower levels of the disease in some Pennsylvania Dutch, Italian, Irish Catholic, and French Canadian descent, especially those living in the Cajun community of Louisiana and the southeastern Quebec.
[23] Gaucher's disease can cause brain damage and seizures, but these effects are not usually present in the form manifested among Ashkenazi Jews; while those affected still bruise easily, and it can still potentially rupture the spleen, it generally has only a minor impact on life expectancy.
The occurrence of several lysosomal storage disorders in the same population suggests the alleles responsible might have conferred some selective advantage in the past.
[52] Prenatal testing for several genetic diseases is offered as commercial panels for Ashkenazi couples by both CIGNA and Quest Diagnostics.
[54] However, this program has been criticized for exerting social pressure on people to be tested, and for screening for a broad range of recessive genes, including disorders such as Gaucher disease.
[4] Hebrew University Professor Raphael Falk published a criticism of studies identifying genetic disorders as being the result of hereditary endogamy.
[55] Dr. Sherry Brandt-Rauf of the University of Illinois and Sheila Rothman of Columbia University co-authored a critique of the methodologies as well as condemning those who worked on the eugenic studies which attributed genetic disorders to religious demographics in paper which explored the ramifications of such concepts entering the workplace stating, "such linkages 'exaggerate genetic differences among ethnic groups' and may result in 'health disparities' in groups not targeted for screening.
In a peer-reviewed medical study, a team of researchers from 23andMe, one of whom (Noura Abul-Husn) is an Associate Professor of Medicine and Genetics at the Icahn School of Medicine at Mount Sinai, criticized guidelines and policies that restrict Tay-Sachs genetic screening to Jews, French Canadians, and Cajuns.
[57] This team found that 59.4 percent of their data pool of 22,681 participants who carry one Tay-Sachs-causing variant on one side of their pair of relevant chromosomes "did not self-report [a] qualifying ethnicity" (one of the three aforementioned populations).