If you ask people to pick from a list of common symptoms, only 3% report that they have one. The larger numbers are mostly or entirely what happens when people are asked if there is anything wrong with them at all, and would they like to blame it on Covid-19.
Also the percentages declined a lot over time, so chances are few of the cases would be permanent or semi-permanent. Even if you buy one of the larger numbers, this is a substantial improvement.
The result that I mentioned in that original comment was the one for rates of ‘some limitation’ of daily activities, not just if they had long covid at all. I could tell a story where the 7.5% number (which was indeed declining, though slowly, since it was still at 6% after 24 weeks) is a better estimator than the 3% (which declined to 1% by 19 weeks) rate of specific symptoms.
The study didn’t list ‘brain fog’ as a symptom, so if people are fairly honest in saying whether their daily activities are limited, and mostly they’re limited by things like brain fog that didn’t appear on the symptom list, the rate could look more like that 7.5%.
The 12 symptoms in our survival analysis approach do not include all those often associated with long COVID such as heart palpitations, chest pain, sleep disruption, cognitive impairment, and depression and anxiety. This may have downwardly biased the estimates. We are exploring options for adding additional symptoms to the CIS questionnaire to address this gap.
And then they give some reasons to think that the higher estimates are more accurate because long covid relapses:
The self-reported long COVID response may better capture the relapsing nature of long COVID symptoms. Of participants who were classed as experiencing symptom discontinuation (two successive symptom-free visits) in our survival analysis approach in Section 4, 14.1% reported at least one of the 12 symptoms in a subsequent follow-up visit. Some of these participants may still describe themselves as having long COVID in our analysis in Section 5 if, from their past experience, they expect periods of improvement to be followed by relapse.
Furthermore, the percentage of participants with symptoms persisting for at least 12 weeks using the survival analysis approach increased to 6.1% when we defined symptom discontinuation as being three rather than two successive symptom-free visits (see the data tables) for full sensitivity analysis results).
It is also likely that the 12 symptoms included in the survival analysis approach do not include some symptoms often associated with long COVID, which may further explain the disparity between the estimates.
On the other hand, are we getting into ‘dragon in the garage’ territory at this point? If long covid is really nonspecific, comes and goes and random and can only be accurately assessed with subjective reports, you’ve just introduced a few huge sources of upward bias.
So overall, I’d treat that 7.5% as an upper limit and the 3% as a lower limit on rates after 12 weeks.
The result that I mentioned in that original comment was the one for rates of ‘some limitation’ of daily activities, not just if they had long covid at all. I could tell a story where the 7.5% number (which was indeed declining, though slowly, since it was still at 6% after 24 weeks) is a better estimator than the 3% (which declined to 1% by 19 weeks) rate of specific symptoms.
The study didn’t list ‘brain fog’ as a symptom, so if people are fairly honest in saying whether their daily activities are limited, and mostly they’re limited by things like brain fog that didn’t appear on the symptom list, the rate could look more like that 7.5%.
However, I’m not sure if I buy this argument. The study authors mention it briefly:
And then they give some reasons to think that the higher estimates are more accurate because long covid relapses:
On the other hand, are we getting into ‘dragon in the garage’ territory at this point? If long covid is really nonspecific, comes and goes and random and can only be accurately assessed with subjective reports, you’ve just introduced a few huge sources of upward bias.
So overall, I’d treat that 7.5% as an upper limit and the 3% as a lower limit on rates after 12 weeks.