COVID-19 was full of surprises early on, causing mild problems in the short term for some people and serious complications for others.
Long term, it may be just as capricious.
Studies are spotting potential heart and brain problems up to a year after infection with SARS-CoV-2, even in people who had mild COVID-19.
The possible long-term effects include "a myriad of symptoms affecting different organs," said Dr. José Biller, director of the COVID-19 neurology clinic at Loyola Medicine in Maywood, Illinois. "So, it could be the lungs, it could be cardiovascular, it could be the nervous system, it could be mental health or behavioral problems."
Estimates vary widely on how many people may be affected. Research suggests about 10% to 20% of people experience mid- or long-term issues from COVID-19, according to the World Health Organization.
That may sound small, but COVID has affected hundreds of millions of people, said Dr. Siddharth Singh, director of the post-COVID-19 cardiology clinic at the Smidt Heart Institute at Cedars-Sinai Medical Center in Los Angeles. In the U.S. alone, about 80 million people have been infected with the coronavirus since the pandemic started in early 2020.
There are many more questions than answers, including about who is most at risk for post-COVID problems and how long the effects might last. But experts say people who have had COVID-19 should be aware of these potential risks:
Heart disease and stroke
A study published in Nature Medicine in February concluded the risk of heart problems one year after COVID-19 infection is "substantial."
Those heart problems include irregular heartbeats, heart failure (the inability of the heart to pump properly), coronary disease (buildup in arteries that limits blood flow), heart attacks and more.
The study included 153,760 U.S. veterans, most of them white and male, who tested positive for COVID-19 between March 1, 2020, and Jan. 15, 2021, and survived at least 30 days. They were compared to a control group of more than 5.6 million veterans without COVID-19.
Researchers adjusted for pre-existing conditions and found that after one year, those who had COVID-19 were 63% more likely to have some kind of cardiovascular issue, resulting in about 45 additional cases per 1,000 people.
Risks were elevated even among people who did not have severe COVID-19. That matches what Singh has seen in his post-COVID clinic, which began treating patients in December 2020. "A lot of patients that we have seen with long-haul symptoms had minor illness and had been treated at home."
Singh also treats many people with postural orthostatic tachycardia syndrome, or POTS, which can cause dizziness, fainting and heart palpitations. "These palpitations mostly tend to happen when people are standing or sitting upright," he said.
In rare cases, "smoldering inflammation around the heart or in the heart" can occur, Singh said.
The Nature Medicine study also found a 52% increased risk of stroke at one year among COVID-19 survivors, or about four extra strokes per 1,000 people.
Among the 113 patients in Biller's long COVID clinic, almost 3 in 4 reported so-called brain fog. "They are unable to multitask, and have difficulties in learning new skills," said Biller, who also leads the department of neurology at the Loyola University Chicago Stritch School of Medicine.