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Comment by odyssey7 | Hacker News Reader

Does everybody with two copies get Alzheimer’s? If not, then there must be at least one additional ingredient / cause.

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> Not only were people with two copies of the APOE4 gene much more likely to develop the biological changes that lead to Alzheimer’s disease, similar to people with the other genetic forms of the disease, they were almost assured the diagnosis: Nearly 95% of the people in the studies with two copies of the APOE4 gene had the biology of Alzheimer’s disease by the time they were 82 years old.

What percentage of people have microplastics in their body? Or have been previously infected by common childhood illness? I’m not giving these as theories for Alzheimer’s etiology, but to show that some environmental factors are ubiquitous.

Just because an environmental factor is ubiquitous—-or is ubiquitous within the frame of some sampling bias for the study—-doesn’t mean we should conclude the cause does not exist.

If a person is given an IV line, wouldn't friction introduce micro plastics into their body?

> What percentage of people have microplastics in their body? Or have been previously infected by common childhood illness? I’m

Unless 95% of these populations also are assured an Alzheimer's diagnosis by 82, your chosen confounding statistics may have little bearing on how closely double copies of the APOE4 gene is associated with Alzheimer's diagnoses.

Their point is that if 100% (for the sake of argument) of the population contains microplastics, and the combination of that PLUS the two genes, equals Alzheimers, then the microplastics was still a cause, it's just that in reality, given the entire population now has the first factor, the gene is what is appearing as the sole contributing factor. But that doesn't mean we can rule out other (albeit ubiquitous) environmental factors as additional contributing (or perhaps even required) causes.

Put another way - and to your point - it's disingenuous to highlight correlation and completely dismiss possible causation. Simply put, that's not The Scientific Method.

The genes might have a trigger. To ignore that possibility is foolish (to put it kindly).

Science shouldn't do this. And (real) journalism should know better as well.

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