Six percent of workers who filed workers’ compensation claims for catching COVID-19 between March 2020 and September 2021 have also received care for Long COVID, according to a new report.

Of these workers, many of them continued receiving medical care for ongoing symptoms a year after their infections, researchers at the Cambridge-based Workers Compensation Research Institute say, citing work that involved data from 31 states.

“Our main takeaways for workers’ compensation policymakers and stakeholders are that long COVID continued to affect a meaningful share of workers with COVID-19 infections, and that was an important driver of claim costs,” said Ramona Tanabe, president and CEO of WCRI.

Symptoms of Long COVID include continued fatigue, fever, heart palpitations and chest pain, shortness of breath, headache, sleeping problems, depression or anxiety, change in smell or taste and difficulty thinking or concentrating, sometimes referred to as “brain fog,” according to the Centers for Disease Control and Prevention.

Among all 50 states, Massachusetts was found to have the second fewest amount of workers who filed Long COVID claims, behind Missouri.

About 3% of workers in the state filed claims for Long COVID care. Oregon, with the most claims in the country, had about 10% of sampled workers who continued to be affected by the virus.

“In states with a higher percentage of workers who received medical care after COVID-19, a lower percentage of those workers with medical care developed long COVID,” the study says.

Legislation sponsored by state Sen. Jo Comerford, a Northampton Democrat, would create a special commission to study Long COVID-related needs in Massachusetts.

The report showed that those treated in the ICU during their initial COVID-19 infection were likely to end up seeking treatment for continued symptoms in the post-acute stage of the infection. Among workers sampled who received ICU care, 74 percent also received treatment for Long COVID.

Of the workers who were hospitalized, but did not receive ICU care, 46% also had Long COVID symptoms; and among those sampled who received one day medical care and no hospitalizations, 5 percent sought treatment for Long COVID.

The cost of Long COVID claims also far outgrew insurance costs to treat initial COVID infections, according to the study.

“At an average of 18 months of post-infection experience, these workers received more than 20 weeks of temporary disability benefits and received about $29,000 in medical care,” Tanabe said.

The medical costs for workers who were hospitalized or had ICU care early after the infection averaged $66,000 and $190,000, respectively.

In comparison, those who were just treated for an initial COVID infection racked up $2,300 in claims.

Most workers with Long COVID had conditions related to their lungs -- with 64% of claims having to do with pulmonary health. A third of all claims had to do with heart-related symptoms, and 12% listed mental health conditions.

About half of the workers with Long COVID had medical bills with continued symptoms affecting multiple parts of their body, the report says.

“Workers with long COVID on average had five months of temporary disability benefits within an average of 18 months of experience after infection. This suggests that in many cases workers with long COVID were not able to return to work after the acute stage of the COVID-19 infection was over, or perhaps they had subsequent absences from work after initially returning to work. Importantly, these measures suggest that long COVID may have had a persistent impact on workers’ ability to work after infection,” the study’s authors wrote.

The sample reflected some correlation between workers’ age and Long COVID. Only 2% of workers 15-24 reported Long COVID symptoms -- with each increasing age group showing higher numbers of people continuing to suffer from symptoms.

Of the 45-54 year olds sampled, 9% reported receiving Long COVID treatment, and 12% of those aged 65 and older did.