About 1 in 4 Americans over age 65 and 1 in 5 adults under 65 experienced “long COVID” or “post-COVID” symptoms after surviving a coronavirus infection, according to a new study from the CDC.

In addition, COVID-19 survivors had twice the risk for developing respiratory conditions and pulmonary embolism.

“As more persons are exposed to and infected by SARS-CoV-2, reports of patients who experience persistent symptoms or organ dysfunction after acute COVID-19 and develop post-COVID conditions have increased,” the study authors wrote.

The research team analyzed electronic health records from a large national database, which included about 353,000 COVID-19 patients and 1.6 million patients without COVID-19, between March 2020 to November 2021, before the Omicron variant surge happened. They looked at 26 conditions, including problems with the heart, lungs, kidneys, and gastrointestinal tract, as well as pain, fatigue, loss of smell or taste, and mental health issues.

Researchers found that 38% of COVID-19 survivors “experienced at least one incident condition” in the months after their infection. In comparison, about 16% of people who weren’t infected were diagnosed with those conditions.

The most common symptoms after a coronavirus infection were “respiratory symptoms and musculoskeletal pain.” Other major symptoms included kidney failure, heart problems, blood clots, and vascular issues.

Among ages 65 and older, researchers found an “increased risk for neurological conditions” and other mental health issues such as mood disorders and substance abuse.

Previous studies have found different estimates for the proportion of COVID-19 survivors who face long COVID symptoms, ranging from 20% to 50%, according to CBS News. The differences likely stem from the different ways that researchers have defined “long COVID” or “post-COVID” in their studies, as well as the different types of symptoms and the different time intervals studied during the pandemic.

The CDC is supporting several ongoing studies to better understand the long-term effects of contracting COVID-19, CBS News reported. Earlier this month, the CDC updated its guidance on post-COVID, adding conditions such as anxiety and depression to the list of possible long-term symptoms.

The CDC has said that more research is needed to understand how to treat patients with long COVID or post-COVID syndromes, CBS News reported. The Biden administration is slated to release two plans related to long COVID in August, which could include potential treatments and therapies.

“Implementation of COVID-19 prevention strategies, as well as routine assessment for post-COVID conditions among persons who survive COVID-19, is critical to reducing the incidence and impact of post-COVID conditions, particularly among adults aged ≥65 years,” the CDC study authors wrote.