What is a comorbidity?
The term itself sounds scary — after all, the word "morbid" is in there. But comorbidities means there are multiple medical conditions that occur in the same person.
Cathy Beckwith, 56, of Jersey Village, Texas, has psoriasis, psoriatic arthritis and has pre-diabetes. She also has premature ventricular contractions, causing an irregular heartbeat.
Her doctors believe her many health conditions are related, and they have a common theme — inflammation. When she visited her cardiologist in Houston, "he told me my (premature ventricular contractions) could be caused by stress on my heart from the inflammation I have all the time," Beckwith said. Once Beckwith's rheumatologist learned she had psoriasis, the doctor was certain her joint pain and swelling were psoriatic arthritis.
Doctors have long suspected that those with psoriasis and psoriatic arthritis, both inflammatory conditions, are more susceptible to a number of related conditions, including obesity, heart disease and diabetes.
Does psoriasis cause comorbidities?
Doctors can't say whether it's the psoriasis that causes the related conditions, also known as comorbidities, or whether it's the other way around. But new research adds to the belief that those with psoriasis are at an increased risk of developing other inflammatory conditions, even those with mild psoriasis.
"We know from experiments with mice that skin inflammation comes first," said Nicole Ward, an associate professor of dermatology at Case Western Reserve University in Cleveland. "It precedes the vascular inflammation that can lead to cardiovascular comorbidities such as heart attacks."
While Ward's lab results in mice are similar to those found in humans by researchers Dr. Nehal N. Mehta, a cardiologist, and Dr. Joel Gelfand, a dermatologist, "we still don't know if it's cause and effect," Ward said. "If psoriasis caused obesity, all psoriasis patients would be overweight, and that's not the case. Likewise, diabetes doesn't cause psoriasis, or everyone who has diabetes would have psoriasis."
Still, Ward said, research has shown that the longer a patient has psoriasis, the greater the risk for developing cardiovascular diseases, diabetes and other comorbidities.
"So you want to treat your psoriasis and inhibit skin disease as quickly as possible," Ward said.
However, even if skin looks clear, that does not necessarily mean the psoriasis is in remission, and internal systemic inflammation may remain. As a result, even if the skin is under good control, it is still critical to see a primary care doctor to ensure other risk factors and comorbidities are monitored.
Mehta said that psoriasis is definitely in play when it comes to the risk of comorbidities.
"We know there is a link," said Mehta, who heads the Section of Inflammation and Cardiometabolic Disease at the National Institutes of Health and was the first to study the relationship among psoriasis, systemic inflammation and vascular disease. Indeed, he said, research has shown that as psoriasis becomes more severe, patients have more diabetes, obesity and cardiovascular diseases.
Elaine Manganello, 61, of northern New Jersey, has no doubt there is a link. She was diagnosed with psoriasis about five years ago, and also has fibromyalgia, high cholesterol, high blood pressure and is about 150 pounds overweight. And while her doctors haven't suggested that her many health conditions may be related, she is convinced they are.
"From what I've read, doctors believe there is a correlation between obesity and fibromyalgia, and a correlation between obesity and psoriasis, and that both are related to inflammation."
Comorbidities increase with severity
Like her colleagues, Dr. April W. Armstrong, a dermatologist and researcher with the University of Colorado, Denver, suspects inflammation is at the root of not only psoriasis but many of its comorbidities.
"Research shows there could be some inflammatory process that's common to psoriasis, as well as other comorbidities," she said.
Armstrong was the lead author of a study published in the journal Dermatology in May 2012. Based on National Psoriasis Foundation surveys among 5,604 psoriasis patients from 2003 to 2011, "Psoriasis Comorbidities" was the largest study to date that used body surface area to measure psoriasis severity and its relationship to comorbidities. The study found that the more severe the psoriasis, the greater the odds of developing comorbidities.
"Our study found that patients with severe psoriasis were 1.5 times more likely to report having heart diseases, compared to those with mild to moderate psoriasis," Armstrong said.
The study also found that patients with severe psoriasis — defined as more than 10 percent of body surface area coverage — are more likely to have diabetes compared to those with mild to moderate disease. In addition, psoriatic arthritis occurs more frequently in patients with severe psoriasis, and patients usually have psoriasis first.
The important message of the study, Armstrong said, is that patients with psoriasis should not only treat their skin disease but also be tested for comorbidities.
Mehta agrees, saying the link is there.
"The key message should be, even though we do not know how and why this link occurs, we know it is there, so be educated to look for your own risks and get assessed," Mehta said.
The role of lifestyle
As a cardiologist, Mehta recommends people with psoriasis lead a lifestyle that can help reduce the risk of heart disease and obesity, two of the most common comorbidities. That entails maintaining a healthy weight, not smoking, eating a low-fat diet rich in fruits, vegetables and lean protein, and getting regular exercise.
"We know from large studies in cardiology that when one controls risk factors for heart disease, such as cholesterol, smoking and blood sugar, inflammation in the body goes down," Mehta said.
But controlling those factors can be difficult. Manganello said that, for her, the conditions feed on each other. Because she's in pain from fibromyalgia, she has difficulty moving. Being sedentary leads to weight gain. Weight gain causes stress, making her psoriasis worse. Manganello has scheduled a gastric bypass for February and is hoping her health will improve as she loses weight, but in the meantime, she's watching her diet and eating foods that don't promote inflammation.
Impact of biologics
Dr. Elizabeth Prater, a dermatologist specializing in medical dermatology at Integris Health in Oklahoma City, said it's important that dermatologists discuss risk factors for coronary artery disease with psoriasis patients.
"There is a growing body of evidence to support the idea that certain treatments for severe psoriasis may be better for patients with coronary artery disease," she said. Because atherosclerosis — hardening of the arteries — and psoriasis are both inflammatory diseases, Prater said that decreasing the overall inflammation may be beneficial to both problems.
"Several recent studies have shown promising results that treatments aimed at reducing tumor necrosis factor-alpha may reduce the risk for heart attack and stroke in patients with psoriasis, but randomized controlled studies are needed to prove this," Prater said.
Dr. Jashin J. Wu, director of dermatology research and associate residency program director in the department of dermatology at Kaiser Permanente Los Angeles Medical Center, is the lead author of the study in the Archives of Dermatology in November 2012 that found psoriasis patients who were on drugs that block tumor necrosis factor-alpha (TNF-alpha), a molecule associated with psoriasis inflammation, had a much lower risk of heart attacks compared to patients whose psoriasis was treated with topical agents.
Wu said that a second article published in the Journal of Internal Medicine a month after supported his findings. However, he said, because both studies looked backward in time, "the most we can say is that there is an association of (TNF-alpha) inhibitor use and the reduction of myocardial infarction (heart attack) risk."
Wu agreed with Prater that long-term studies are needed to fully explain the relationship between TNF-alpha inhibitor use and heart attack risk in psoriasis patients.
For her part, ever since Beckwith learned she had pre-diabetes, she has been monitoring her blood sugar and eating a diet of mostly fruits, vegetables, whole grains and lean protein. She stopped drinking soda and other drinks high in sugar, and so far, she hasn't crossed the line into a diabetes diagnosis.
Beckwith, who has been taking methotrexate for her psoriasis since February 2013, finds the treatment also helps her psoriatic arthritis. And her heart condition has been under better control since her doctors, working together, have reduced her inflammation.
"I had three episodes in less than a year where I had to go to the hospital, and now I haven't been in the hospital since the start of the year," she said. "I feel a million times better."