Long covid linked to air pollution exposure in young adults - new study

Although covid-19 infections are usually less severe in young adults, this does not mean that they are not still at risk of complications from covid-19. For example around one in 25 adults over 16 have reported suffering from prolonged covid-19 symptoms after their first infection. For some, these symptoms lasted almost two years.

While we are getting closer to understanding some of the genetic and immunological mechanisms that causes long-term covid, there's still a lot we don't know about the condition — including why people with otherwise mild covid-19 infections go on to develop long-term covid.

We also know some of the risk factors that make people more likely to develop long-term covid - including suffering from chronic diseases and have one unhealthy lifestyle. And our latest study has now revealed that, at least for young adults aged 26-28, where they live can increase the risk of long-term covid.

While most people recover from a covid-19 infection after a few weeks, their symptoms may persist for some people persist for months or even years afterwards. The most common symptoms include extreme fatigue, loss of smell (or taste), muscle aches and shortness of breath, although other symptoms - such as brain fog - have also been reported. Although there is no single test for long-term COVID, a doctor can diagnose the condition through blood tests, blood pressure checks, or chest x-rays.

Our study found that young adults who lived in highly polluted areas were more likely to suffer from prolonged covid compared to those living in areas with low levels of pollution.

Air pollution and covid-19

In our latest study, published in Lancet Regional Health Europewe investigated the effect of long-term exposure to air pollution on the risk of long-term covid in young adults.

To conduct our study, we used data from the ongoing BAMSE birth cohort. This study began in 1994 in Stockholm County, Sweden and recruited 4,000 newborns – many of whom are still followed today. Participants were given frequent questionnaires and participated in clinical examinations during childhood and adolescence to track various aspects of their health.

Between August 2020 and February 2022, the participants took part in a covid-focused follow-up. Among the 753 study participants who had covid, nearly one in six who had a mild or moderate infection reported suffering from persistent symptoms for two months or more. The most common persistent symptoms reported were altered sense of smell or taste, shortness of breath, and extreme fatigue.

We then estimated level of air pollution participants were exposed to before the pandemic by looking at pollution levels at their residential addresses. We found that being exposed to relatively high levels of air pollution in 2019 - especially fine particulate air pollution, which is mainly from traffic - was linked to a 28% greater likelihood of having long-term covid compared to those living in low pollution areas.

This association remained even after taking into account other factors potentially linked to both greater covid risk and exposure to air pollution - including socioeconomic status, whether they smoked, and whether they had any other health conditions (such as asthma).

The association between air pollution and the likelihood of developing long-term covid was also stronger for specific long-term covid symptoms — especially those related to respiratory health, such as shortness of breath.

Air quality

Air pollution is the fourth leading cause of death worldwide. It is connected to several diseasesincluding asthma, chronic obstructive pulmonary disease and stroke, as well as COVID 19.

Our study is now the first to link exposure to air pollution with long-term covid in young adults.

It is currently unknown why air pollution may be linked to prolonged covid. But based on what we know from other studies about the harms of air pollution, one potential explanation could be that air pollution triggers inflammation in many tissues and organs of our body. Although inflammation is the body's way of protecting itself against harmful pathogens – such as bacteria or viruses – it can also be harmful and destructive to the body itself. Thus, long-term inflammation linked to exposure to air pollution may trigger the range of symptoms that people report experiencing with long-term covid.

But it will be important to continue to explore other possible mechanisms, including genetic and immunological factors, that explain why people living in highly polluted areas are more likely to develop prolonged covid. It will also be important to investigate whether there is a similar relationship between air pollution and long-term covid in other age groups.

And because our study was conducted before most participants had received the Covid-19 vaccine, future research will need to take this into account and evaluate whether vaccination changes this association at all. These will be the focus of our next follow-up study with this cohort.

We hope our findings will increase our understanding of long-term covid, which in turn can help us better know how to diagnose and treat the condition. Our research also adds to the current body of evidence showing how harmful air pollution is to human health. Given that everyone is exposed to air pollution in some way during their lifetime, it is clear that more needs to be done to reduce air pollution levels worldwide to improve all aspects of health.

Author: Zhebin Yu - Postdoctoral fellow in environmental medical epidemiology, Karolinska Institutet | Erik Melen - Professor of Pediatrics, Karolinska Institutet | Sandra Ekström - Postdoctoral researcher in epidemiology, Karolinska Institutet

https://nord.news/2023/03/07/long-covid-linked-to-air-pollution-exposure-in-young-adults-new-study/?feed_id=15553