The language there is weird ("fold" is always an ambiguous way to express relative increases, but it's especially weird here). I assume that means a 60% higher chance?
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.
"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.
