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Comment by omnicognate | Hacker News Reader

I can't think of any other way to interpret it. A x-fold increase of y is x times y.

Seems Wikipedia agrees, so that's something:

https://en.wikipedia.org/wiki/Fold_change

In which case a 60% increased probability is a very significant increase. Seems like a valid thing to test for when assessing someone for long COVID, given it still remains somewhat of a diagnosis of exclusion.

it's a relative risk, and the underlying absolute risk was very small, so even if 60% sounds big, testing everybody isn't the right solution.

IIRC the absolute risk of long Covid is 7-15% per infection, which is anything but very small.

if that's true, and people get reinfected periodically, then basically everybody will have long covid :)

but not really. what you're seeing is that some fraction of the populace is susceptible to long covid (risk factor or genetic).

"Increase" is ambiguous here. If I said a 160% increase, that is typically taken to mean that the new value is 260% of the original. So "1.6-fold" could mean the same, or it could mean 160% of the original.

No, the "-fold increase" form specifically means multiplying by that value, not adding that multiple of the value. A "3-fold increase" always means increasing to 3 times the original value, not adding 3 times the original value (which would be a 4-fold increase). See [1], the wiki link in the sibling comment to yours and many other results from googling "fold increase".

The percentage variant, in contrast, is indeed ambiguous, the "60% increase" mentioned in the comment I responded to ironically only being unambiguous because the purely multiplicative interpretation (going to 60% of the value) would be a decrease. Such ambiguous use of percentage changes is common and annoying, and it would be good to see more use of the unambiguous "x-fold increase" wording.

[1] https://www.collinsdictionary.com/dictionary/english/fold-in...

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