The great foreskin fallacy: autism by circumcision? Not even close.
Slicing through the baloney behind RFK Jr.'s circumcision-autism claims. We've heard some pretty absurd claims from HHS Secretary RFK Jr., but his claim that circumcision, possibly in combination with Tylenol, might cause autism is a cut below the rest. You wouldn't think that circumcision, a 4,000-year-old practice, would be a hot news topic. You'd be wrong. To the dismay of Jewish and Muslim organizations, the UK recently created guidelines that classified certain non-therapeutic circumcisions as possible child abuse. More recently, Belgian prosecutors indicted 3 mohels (circumcisers) in connection with a long-running investigation into allegedly illegal circumcisions in Antwerp. RFK Jr. claims that circumcised boys can have up to double the rate of autism compared to boys with their foreskin.
To support his claim, he cites 2 papers, one a Danish study & the other a population study. But the "evidence" rests largely on statistical measures called hazard ratios (HR). In simple terms, an HR compares how often a particular outcome occurs in one group vs. another over time. In the Danish study, they reported an HR of 1.46, meaning a 46% higher rate of autism spectrum disorder in the circumcised group, while the other study reported an HR of 2, double the rate of autism vs. the non-circumcised group. The numbers may sound scary, but the studies are retrospective (looking backward searching for statistical associations) & observational.
Such studies are much more vulnerable to confounders (hidden factors & researchers repeatedly searching huge databases until a statistical pattern appears). If you search through enough data, you're bound to come up with something that inevitably produces impressive-looking correlations that are completely meaningless. They do not prove cause & effect, which is why the gold standards of science are based on randomized, placebo-controlled, double-blind studies. Retrospective observational studies do not randomize anything.
Hazard ratios (HR) of 1.46 to 2 may seem high, but when compared to the HR between smoking & lung cancer, they pale in comparison, which has an HR of 20; that's a 10 to 40-fold difference. In other words, the circumcision association link is weak. Furthermore, the Danish study has incomplete circumcision records, incomplete autism diagnoses, no sibling comparison, & no genetic controls. Strong statistical relationships have been shown with shoe size & cancer risk, ice cream consumption & arthritis, or birth month & heart disease. A famous example shows an almost perfect correlation between the number of babies given the name Eleanor over 25 years & the amount of electricity generated by Polish wind farms. Despite powerful statistical correlations, there is obviously no plausible connection between babies named Elanor & wind power generation in Poland, just as there is no known biological pathway connecting the removal of the foreskin to autism. There is no hormonal mechanism, no immune mechanism, no neurological mechanism, & no plausible timing window. Without biological plausibility, weak associations are presumed spurious, at best.
Weak associations are notoriously unreliable. Denmark is strongly associated with specific religious & immigrant populations that differ from the general population in many ways unrelated to circumcision itself. Differences in healthcare access, socioeconomic status & cultural attitudes towards diagnosis & developmental screening can all influence autism statistics independently of circumcision. Denmark's registry is excellent, but circumcision is rare (1-5%). Small exposure groups, & incompl,ete data can inflate hazard ratios. Many ritual circumcisions in Denmark occur outside hospitals. If researchers can't determine who actually belongs in the circumcised group, the resulting hazard ratios become far less trustworthy & may ultimately be meaningless. The studies RFK Jr. cites are demonstrably weak. The link between circumcision & autism is patently ridiculous. Just ask Elanopr. Last I heard, she was in Poland.
