Study links long COVID-19 to surge in new chronic illnesses in Estonia
A new study based on data from Estonian residents shows that long COVID and chronic illnesses have a direct two‑way connection. Existing chronic diseases prolong COVID symptoms, which in turn paves the way for diagnoses such as sleep apnea and heart rhythm disorders.
Researchers at the University of Tartu reached this conclusion after analyzing the health and genetic data of nearly 210,000 Estonian Biobank donors. They compared the medical histories of more than 2,000 people with long COVID to roughly 200,000 individuals in a control group.
The analysis revealed several links. First, long COVID most often affected people aged 40–59, and three‑quarters of those with prolonged symptoms were women. The risk of long COVID was significantly increased by overweight, previous chronic kidney disease, asthma, and type 2 diabetes. For chronic obstructive pulmonary disease (COPD), the risk of persistent symptoms was more than twice as high as usual.
The chain also worked in the opposite direction. During the pandemic years, doctors diagnosed new health problems much more frequently in patients with long COVID. For example, the risk of sleep apnea — nighttime breathing interruptions — was three times higher than before. Heart rhythm disorders and thyroid diseases also became more common. Researchers do not entirely rule out the possibility that people with long COVID simply visit doctors more often and therefore receive more diagnoses.
The scientists paid special attention to type 2 diabetes. The study showed that starting in spring 2020, the number of new diabetes cases in the general population began to rise sharply, exceeding all previous mathematical projections. Genetics also played a clear role: those with a higher genetic predisposition to severe COVID developed diabetes 17 percent more often.
Why is this happening? According to researchers, the virus damages the body on several fronts. Existing chronic diseases create a favorable environment for inflammation and immune system disturbances, preventing full recovery from infection. The rise in new diabetes cases may reflect the virus's impact on the pancreas — the organ that produces insulin, which regulates blood sugar.
Pandemic‑era lifestyle also strongly contributed to the development of new illnesses. People moved less, stress increased, and body weight rose.
The researchers published their findings in the journal Frontiers in Public Health.
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Editor: Andres Reimann, Argo Ideon
