[mulvya]

> Kind of hard to tell what this result means without a control or baseline

Yes. As pointed out in

Causation or confounding: why controls are critical for characterizing long COVID

https://www.nature.com/articles/s41591-021-01402-w

"To address some of these biases, we and others used established longitudinal cohorts recruited at the start of the pandemic for regular testing for antibodies to SARS-CoV-2 and thus provided objective confirmation of infection. We asked our healthcare-worker participants about 72 symptoms reported to be associated with long COVID, at a median of 7.5 months after the development of COVID-19, and found that mental-health, gastrointestinal and dermatological symptoms were as common among 140 patients with mild-to-moderate symptomatic seropositive COVID-19 (‘cases’) as in 1,160 control participants who remained asymptomatic and seronegative throughout the surveillance period. Of concern, 40–60% of both cases and control participants reported mental-health symptoms, which highlights the toll of pandemic on the healthcare workforce. We also identified three clusters that included 12 symptoms—affecting the sensory, neurological and cardiorespiratory systems—that were reported by 67% of cases but also 44% of control participants, which emphasizes the ongoing difficulties in characterizing long COVID."