Abstract Previous studies on the natural history of long-COVID have been few and selective. Without comparison groups, disease progression cannot be differentiated from symptoms originating from other causes. The Long-COVID in Scotland Study (Long-CISS) is a Scotland-wide, general population cohort of adults who had laboratory-confirmed SARS-CoV-2 infection matched to PCR-negative adults. Serial, self-completed, online questionnaires collected information on pre-existing health conditions and current health six, 12 and 18 months after index test. Of those with previous symptomatic infection, 35% reported persistent incomplete/no recovery, 12% improvement and 12% deterioration. At six and 12 months, one or more symptom was reported by 71.5% and 70.7% respectively of those previously infected, compared with 53.5% and 56.5% of those never infected. Altered taste, smell and confusion improved over time compared to the never infected group and adjusted for confounders. Conversely, late onset dry and productive cough, and hearing problems were more likely following SARS-CoV-2 infection. Open access, https://www.nature.com/articles/s41467-023-39193-y
"Furthermore, it is possible that some individuals in the comparison group had SARS-CoV-2 infection that was not detected by a PCR test. This risk was reduced by excluding from the analyses 53,530 participants who had only negative PCR tests recorded but who reported that they had had SARS-CoV-2 infection. However, classification error due to undiagnosed, asymptomatic infection remains." I think this is an extremely relevant point. By now there exists close to nobody that hasn't had at least one Covid-19 infection. As such the type of controls they are claiming to have here, are increasingly getting impossible to come across in the future, especially since PCR testing on a wider scale or even at a small scale doesn't exist anymore. I also believe that it's useful to compare some of these results now that all restrictions have been lifted. It isn't unreasonable to assume that some of the well-being of the uninfected has increased due to this, whilst it is irrelevant to those suffering from Long-Covid symptoms. I don't know how relevant this is, if at all, but to me it's sensible to also ask study participants how often they had been to the doctor in recent months and if any other diseases were detected during that time. Someone with Long-Covid might go to the doctor more often and as such have a higher chances to get treatment for diseases that could possibly be unrelated to Long-Covid. Finally I would once enjoy to see such a study that examines these sort of number in the roughly 2/3 female 1/3 male, younger part of the population. In this population, I would naturally expect greater health if Covid didn't exist. Perhaps older people with many comorbidities related or unrelated to Covid, skew these numbers a bit. It's a bit similar to saying child mortality doesn't exist, because all the people that answered the questionnaire were 18+. Finally those most severly affected by Long-Covid are often too sick to even participate in such studies.
