• According to a report on patient characteristics from Italy's National Institute of Health released on March 17, 99% of Covid-19 patients who have died in the country had at least one preexisting condition. 
  • Nearly 50% of the patients who died had three preexisting conditions.
  • In the US, Covid-19 patients with underlying health conditions were 12 times more likely to die compared to those with none reported, according to CDC data through May 2020.
  • Here's what we know about how much various conditions affect the coronavirus' severity. 
  • Visit Business Insider's homepage for more stories.

Case studies on patients who have contracted the new coronavirus have found that older people and those with preexisting health conditions more commonly develop severe symptoms.

According to a report on patient characteristics from Italy's National Institute of Health released on March 17, at the beginning of the pandemic,  99% of Covid-19 patients who died had at least one preexisting condition. 

Different preexisting conditions — including heart disease, high blood pressure, diabetes, and kidney disease — were found at varying rates among the patients who died.

More recently, data reported to the Centers for Disease Control and Prevention through May 30 showed heart disease, lung disease, and diabetes were among the most common comorbidities with Covid-19. Patients with underlying health conditions were 12 times more likely to die of Covid-19 compared to otherwise healthy patients.

Here's what we know about how various health issues may affect a patient's coronavirus prognosis. 

In the Italian study, 76.1% of patients who died from Covid-19 had hypertension, or high blood pressure.

Nearly half of all Americans have some level of high blood pressure, meaning they may be more susceptible to some of the more dangerous effects of the coronavirus.

According to state data, 56.7% of patients who died of Covid-19 in New York also had high blood pressure. In Lousiana, that number was 59.8% as of April.

In a retrospective study of more than 2800 patients hospitalized with Covid-19 in Wuhan, China, those with high blood pressure were twice as likely to die compared to patients with normal blood pressure.

One-third of Covid-19 patients who died in Italy had heart disease.

Any kind of cardiovascular condition can leave a patient more susceptible to severe disease from the virus.

While experts aren't confident about why people with poor cardiovascular health are at a higher risk of dying from the virus, doctors believe that the strain Covid-19 puts on the lungs may burden the heart as well. 

People with heart issues may also have weaker immune systems, and the virus could have a negative effect on those with plaque in their arteries, according to the American Heart Association.

About one-quarter of people who died from the coronavirus in Italy had atrial fibrillation.

At least 2.7 million Americans are living with atrial fibrillation. It's "a quivering or irregular heartbeat that can lead to blood clots, stroke, heart failure, and other heart-related complications," according to AHA.

Diabetes was the second most common condition among Covid-19 patients who died.

Tom Hanks, who tested positive for Covid-19 along with his wife, Rita Wilson, has Type 2 diabetes. 

The condition may make Covid-19 worse because some viruses thrive on higher blood glucose levels, and people with diabetes also have compromised immune systems, according to Health.com.

In New York, 37.5% of patients who died of CovidD-19 also had diabetes. People with diabetes made up 38.1% of Covid-19 deaths in Lousiana as of April.

Of those who died in Italy, 20.3% had active cancer in the past five years.

Cancer and its treatments can impair the respiratory system and render a person immunocompromised.

The study found that 18% of people who died had chronic kidney disease.

The National Kidney Foundation recommends that patients with kidney disease follow the same advice as the general population: Stay home when possible, be diligent about handwashing and sanitizing surfaces, and make sure you have enough necessary medical supplies. 

Dialysis patients should not miss their treatments, and those who feel sick should alert a member of their healthcare team.

Chronic obstructive pulmonary disease — or lung diseases such as chronic emphysema and bronchitis — was present in 13.2% of the people who died.

People with lung diseases like emphysema or bronchitis have lungs that are weaker when trying to fight off the infection.

When Covid-19 travels through the body, it can attack the lungs. 

The infection causes inflammation in the lungs' lining and irritation in the nerves around them. The virus can also cause inflammation in the air sacs at the bottom of lungs. That can lead to pneumonia — when the lungs fill up with fluid.

Inflamed air sacs also prevent lungs from getting enough oxygen into the bloodstream and removing the byproduct carbon dioxide, The Guardian reported, citing John Wilson, a respiratory physician. Such inflammation can cause vital organ failure and be fatal.

People who previously had a stroke made up 9.6% of Covid-19 patients who died in Italy.

According to the Stroke Association, a stroke itself doesn't put a survivor in immediate danger of the coronavirus. However, many of those who experience strokes fall into other at-risk categories. 

"You're at greater risk of complications if you are an older person, or have a health condition like diabetes, heart disease, respiratory disease or chronic kidney disease," the Stroke Association wrote in a statement. "Having a suppressed immune system or being on some treatments like steroids and chemotherapy may also make you more at risk."

Chronic liver disease was the 10th most common underlying condition among Covid-19 patients who died.

It's unclear how exactly Covid-19 affects the liver, but even people with healthy organs may be at risk for liver injury from the virus, according to The Hospitalist

People with liver transplants who are on immunosuppressing medications may be at great risk but should talk to their doctors before changing or stopping any drug regimen, according to the UK's Liver Trust.

Studies have identified extreme obesity as a risk factor for dying among Covid-19 patients who are male or relatively young.

An analysis of thousands of patients treated at a Southern California health system identified extreme obesity as an independent risk factor for dying among Covid-19 patients. The association was strongest among adults 60 and younger, and particularly among men.

Studies from Columbia University and Public Health England supported this finding, underscoring that obese people are more likely to require ventilation or die if they contract Covid-19.

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