The study noted that there was a noticeable drop in the lung function in the first six months after having mild Covid infection.
The study noticed a 3.9 percent increase in predicted DLCO over about 18 months. (Shutterstock)
Over the past two years, research into the lasting impacts of Covid has unequivocally linked it to cardiovascular disease, gastrointestinal symptoms, and respiratory issues. However, recent findings have broadened our comprehension as it appears that individuals experiencing the prolonged effects of Covid may also undergo a significant decline in lung function.
Researchers in Denmark scrutinised lung function trajectories in mild Covid-19 with two-year follow-up. They further compared the lung health of those who had a mild case of Covid with those who didn’t get infected.
Their investigation revealed a noticeable drop in lung function during the initial six months after experiencing mild Covid infection. Subsequently, the decline persisted but at a slower pace, suggesting a lasting negative impact on lung health with only limited recovery.
Interestingly, around six months post-infection, the decline in lung function began mirroring the typical age-related decline observed in everyone’s lungs.
The study highlighted, “By comparing longitudinal changes in individuals with mild Covid-19 and uninfected controls, our results indicate that mild Covid-19 leads to a significant decline in lung function during the first six months after infection and a slower decline thereafter, indicating lasting decline with limited recovery. However, we observed that the accelerated decline slowed and eventually followed the expected annual age-associated decline approximately six months post-infection.”
When individuals with Covid were compared to those who remained uninfected, the study found an average decline in lung function of approximately 13 mL per year and 33 mL in Total Lung Capacity (TLC) in specific lung measures from before contracting Covid to six months after. After six months, the decline in lung function seemed to revert to the normal age-related decline that occurs as people age. Thus, the results suggest that Covid can cause lasting damage to the lungs with only limited recovery.
Total Lung Capacity (TLC) represents the maximum volume of air present in the lungs after a full inspiration. In healthy adults, the average lung capacity is about 6 litres. Various factors, including age, gender, body composition, and ethnicity, can affect TLC. It is calculated by measuring lung capacities such as inspiratory capacity (IC), functional residual capacity (FRC), and vital capacity (VC), using techniques like plethysmography, dilutional helium gas method, nitrogen gas washout method, or high-resolution computed tomography.
Speaking to South First, Dr Rajeev Jayadevan, Co-Chairman of the National Indian Medical Association Covid Task Force, explained, “FEV1 and FVC (measurable lung function parameters) declined for six months following initial infection, and continued to decline even at two years. The speed of decline levelled off at six months, but failed to improve back to baseline. The accelerated decline among patients slowed at the six-month mark, and eventually followed the expected ‘normal’ age-related decline. But it did not return to baseline.”
Additional findings from the study include a 3.9 percent increase in predicted Diffusing Capacity of the Lungs for Carbon Monoxide (DLCO) over about 18 months, indicating a potential improvement in line with findings from other studies on hospitalised individuals.
DLCO is a measure in pulmonary function tests that assesses how efficiently the lungs transfer gases, especially carbon monoxide, from the air into the bloodstream. It helps evaluate lung efficiency in gas exchange and provides information about alveolar function and surrounding capillaries. Abnormalities in DLCO can indicate various lung conditions.
Despite the average increase in DLCO (lung function) from six to 24 months after a Covid infection, the study did not observe a corresponding decrease in difficulty breathing (dyspnea).
Dr Jayadevan said, “DLCO increased past the six-month mark, but there was no corresponding improvement in breathing difficulty. The timeframe of initial infection was March 2020 to January 2021. This means that the participants were unvaccinated at baseline.”
He added that this decline is ordinarily something we might expect in people hospitalised with Covid pneumonia. But the study excluded hospitalised patients, focusing only on mild Covid. It showed that Covid (in the unvaccinated) can covertly cause lasting lung damage.
Dr Jayadevan explained that lung capacity can decrease after Covid due to various factors, including lung damage and inflammation.
“Covid can cause pneumonia, which leads to fluid accumulation in the lungs and inflammation, resulting in breathing difficulties that might take months to improve. Covid-related bronchitis can cause excessive sputum production in the airways, resulting in coughing and chest congestion. The sputum narrows the airways, further reducing lung capacity,” Dr M Rajeev, Pulmonologist at Gandhi Hospital in Hyderabad, told South First.
He added that studies have also suggested that one-fourth of Covid patients have an impaired pulmonary function after 12 months of disease onset, with older patients, those with more than three chronic conditions, and those with severe cases improving slower than other patients over time.
“We should also care that lung capacity naturally decreases with age, and this decline can be accelerated by factors such as smoking, pollution, and lung diseases,” he said.
Only a few studies have looked into what happens to people’s lungs in the long run after they had Covid, whether they were in the hospital or not, two years after getting sick. These studies give us mixed information.
One study followed 288 people who were in the hospital, and it found that their lung function seemed to get a bit better in the first six months after they got sick. However, from one year to two years after infection, their lung function declined, which they said was normal with ageing.
Another study with 144 hospitalised individuals found a small but noticeable increase in lung function from six to 24 months after getting sick, no matter how severe their illness was.
It’s important to note that both studies didn’t know what these people’s lung function was like before they got Covid, and they didn’t consider other things that can affect lung health. Also, they didn’t compare the results with people who didn’t get Covid.
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