Amish anomaly

The Amish anomaly refers to the low rates of autism spectrum disorders among the Amish, the subject gained widespread attention after being documented by Dan Olmsted for United Press International. Olmsted asserted that he could only find three Amish autistics after searching in Lancaster County, Pennsylvania and that two of them were vaccinated.^[1] Even the critics of Olmsted have found the Amish to have an autism rate 73 times lower than the national average. ^[2][3][4] The statement that autism doesn't exist in Amish populations generally agreed to be an exaggeration, though the rate is a small fraction of that in the surrounding population and by far the lowest in the USA.^[5][6][7] This anomaly is of interest because the Amish effectively constitutes a sizable unvaccinated control group, though less than ideal due to significant dietary, genetic, and lifestyle differences. Some have argued that this anomaly alone constitutes a correlation between vaccines and autism.^[8] This hypothesis has not been thoroughly explored and remains the subject of debate.

Background

In his columns, Olmsted quoted Dr. Frank Noonan as saying, "You'll find all the other stuff, but we don't find the autism. We're right in the heart of Amish country and seeing none, and that's just the way it is."^[9]

Criticism

Ken Reibel, of the blog Autism News Beat stated that, "The idea that the Amish do not vaccinate their children is untrue.” Allegedly, Dr. Kevin Strauss, MD, a pediatrician at the CSC, when contacted by Reibel, reportedly said that Olmsted never visited the CSC, and that he didn't think Olmsted spent much time in Lancaster County.^[10]

Further criticism of Olmsted's reporting comes from David N. Brown, who states that "In March 2006, Drs. Kevin Strauss, Holmes Morton and others documented 9 autistic Amish children, which could raise the autism rate of the Lancaster Amish community Olmsted supposedly investigated to almost 1/5,000 which is still a fraction of the US average of 1/68 ^[11][12][13] The statement that autism doesn't exist in Amish populations generally is an exaggeration, though the rate is a small fraction of that in the surrounding population.^[5][6][7]

Vaccination rates in Amish communities

Similarly, a 2006 study by researchers from the CDC, based on a survey sent to residents of the largest Amish community in Illinois, concluded that the Amish may not object to vaccines very often, and that when they do so, it may not be for religious reasons.^[14] Despite these figures, significant pockets of lower vaccination rates do exist.^[15]

Reasons for the lower Amish vaccination rate

A study published in Pediatrics in 2011 concluded that "The reasons that Amish parents resist immunizations mirror reasons that non-Amish parents resist immunizations."^[15] Reasons that a majority of Amish do not vaccinate as often as most people in developed countries include:

• Some Amish may simply see no benefit that outweighs the known risks ^[16]
• Distrust over safety — some view immunization as putting themselves at risk through exposure to a disease or concerns that live virus vaccines may cause an illness that an isolated population would not otherwise be exposed to
• Some distrust the efficacy of the vaccines.^[17][18]
• Most Amish tend to carefully consider the risks and benefits of medical intervention, trending towards a conservative approach of minimal intervention. ^[19]
• Religious grounds — some Amish see immunization as putting faith in man over God, or that it is an affront to vaccinate against diseases transmitted through unclean lifestyles and sinful behaviors (Gardasil)^[20]

The more conservative of Amish are less likely to seek medical care, and more likely to delay treatment, especially when physical symptoms are absent or minimal.^[21] However, it has been noted that "In health matters, the Amish are pragmatists"^[22]

Amish incidence of measles

In 2014, an outbreak of TYPE B measles (current Vaccination is for TYPE A measles) occurred in an Ohio-based Amish community with among the highest Amish vaccination rates, but still well below US average rates. 382 of the 644 cases nationally that occurred in that year were Amish, 324 of the infected Amish were vaccinated. The disease was introduced by three unvaccinated missionaries, who had traveled to Philippines (which was itself experiencing a major outbreak).^[23]

Alternative explanations

There are alternative explanations for the low Autism/ASD rates in the Amish communities. Autism is thought to have many genetic or epigenetic correlations.^[24] If prevalence of ASDs did vary in a relatively isolated, closed population such as Amish communities, it could be explained by gene pool variations compared the general population. Similarly to Amish having statistically higher rates of some conditions (such as dwarfism, angelman syndrome and metabolic disorders), they could also be expected to have lower rates of some others.^[25]

In addition to likely or established gene pool variations, Amish populations have significantly different lifestyles to the general population.^[26] An example being dietary differences.^[27] Diet and environmental factors are known to significantly impact the make-up of gut microbiomes.^[28] Gut microbiome differences have also been associated with autism.^{[28][29][30][31]} Amish also avoid many modern technologies.^[32] Given the wide range of different lifestyle factors involved, apart from vaccination rate differences, there are many confounding variables to making a causal link to the hypothesised autism prevalence difference. These environmental factors do not have any established link to ASD, but lay be determined to be related in the future.

References