People with nonalcoholic fatty liver disease (NAFLD) are more likely to develop severe infections requiring hospitalization, according to findings from a large Swedish cohort study.
The increased risk was equal to one extra severe infection in every six patients with NAFLD by 20 years after diagnosis, wrote Fahim Ebrahimi, MD, of the Karolinska Institute in Stockholm, and coauthors.
“Accumulating evidence suggests that NAFLD can affect multiple organ systems, which is not surprising, as the liver has multiple functions – regulating metabolism and being a central organ of the immune system,” Dr. Ebrahimi said in an interview.
The study was published online in Clinical Gastroenterology and Hepatology.
“Up to a fifth of cells in the liver are immune cells that process numerous antigens and pathogens from the gastrointestinal tract,” Dr. Ebrahimi noted. “We were intrigued by experimental studies showing that, in NAFLD, many of these key immune cells become dysfunctional at various levels, which may affect disease progression, but at the same time also increase the susceptibility to viral, bacterial, and fungal infections.”
Patients with NAFLD have metabolic risk factors known to increase infection risk, but a smaller study by a different research group had found that NAFLD could independently predispose patients to bacterial infections.
To further explore a connection between NAFLD and infection risk, the researchers looked at data for 12,133 Swedish adults with simple steatosis, nonfibrotic steatohepatitis, noncirrhotic fibrosis, or cirrhosis caused by NAFLD confirmed by liver biopsies performed between 1969 and 2017.
Each patient was matched to five or more contemporary controls from the general population by age, sex, and region of residence. The authors conducted an additional analysis that also adjusted for education, country of birth, and baseline clinical comorbidities, including diabetes, obesity, dyslipidemia, and hypertension, as well as hospitalization preceding the biopsy and chronic obstructive pulmonary disease.
The primary endpoint was severe infections requiring hospital admission. Secondary endpoints included seven prespecified infection subgroups: sepsis; respiratory tract; most gastrointestinal infections; bacterial peritonitis; urogenital; muscle, skin, and soft tissue; and other infections.
Elevated risk at all NAFLD stages
Dr. Ebrahimi and colleagues found that over a median follow-up of 14 years, patients with NAFLD had a higher incidence of severe infections – most often respiratory or urinary tract infections – compared with those without NAFLD (32% vs. 17%, respectively).
Biopsy-confirmed NAFLD was also associated with a 71% higher hazard and a 20-year absolute excess risk of 17.3% for severe infections requiring hospital admission versus comparators. The elevated risk showed up in patients with steatosis and increased with the severity of NAFLD. Simple steatosis saw a 64% higher risk (adjusted hazard ratio, 1.64; 95% confidence interval, 1.55-1.73), whereas patients with cirrhosis saw a more than twofold higher risk, compared with controls (aHR, 2.32; 95% CI, 1.92-2.82).
When Dr. Ebrahimi and colleagues adjusted for parameters of the metabolic syndrome, they found an independent increased risk for severe infection. For patients with NAFLD, the increased risk may come from greater susceptibility to infections in general or to a more severe course of infections.
“Our study clearly demonstrates the complexity and high disease burden associated with NAFLD,” Dr. Ebrahimi said. “We are beginning to understand the different layers involved and will eventually move away from a liver-centric view to a more holistic view of the disease.”
Clinicians caring for patients with NAFLD need to be aware of the increased risk for infection, Dr. Ebrahimi said. They also should assess their patients’ vaccination status, and seek to control modifiable risk factors, such as diabetes.
Nancy Reau, MD, of Rush University, Chicago, described the study’s message as important.
“Patients with NAFLD and advancing liver disease are at risk for severe infections,” Dr. Reau said. “When we consider the fact that patients with advanced liver disease tend to die from infectious complications, awareness leading to early recognition and efficient treatment is imperative.”
The authors acknowledged the following limitations: only severe infections requiring hospitalization could be captured; whether infection led to decompensation or vice versa among patients with cirrhosis could not be determined; and detailed data on smoking, alcohol, vaccinations, body mass, and other potentially relevant measures were not available.
The Swiss National Science Foundation, Syskonen Svensson Foundation, and Bengt Ihre Foundation provided grants to Dr. Ebrahimi or coauthors. One coauthor disclosed previous research funding from Janssen and MSD. Dr. Reau disclosed receiving research support and consulting fees from AbbVie and Gilead, as well as consulting fees from Arbutus, Intercept, and Salix.
A version of this article first appeared on Medscape.com.