Immunosuppression Surprisingly Prevalent in American Adults

Caroline Helwick

November 02, 2016

NEW ORLEANS — More than 4% of adults in the United States report being told by a physician that they are immunocompromised, and almost 3% say they currently are, a new analysis of survey data shows.

Immunocompromise is associated with the reactivation of chronic infections, increased risk for opportunistic infections, the inability to receive vaccinations, and other potential health problems.

The emergence of potentially immunosuppressive therapeutics has likely led to an increase in the number of adults who are immunocompromised, but the size of this population has been unclear, said Rafael Harpaz, MD, MPH, from the Centers for Disease Control and Prevention.

Statistics are available for people living with HIV or who have undergone kidney transplant, for example, but many people are immunocompromised as a result of the use of common medications, such as corticosteroids.

"Now we have more and more people with indications for biologics, transplants, and so forth," Dr Harpaz told Medscape Medical News. "And they are living longer because we are managing them better. It's all changing, and no one has had a clue about the numbers — what they are, and where they are going.

"We've been asleep at the wheel," he said here at IDWeek 2016.

To address the issue, he and his colleagues conducted a cross-sectional analysis of data from the 2013 National Health Interview Survey (NHIS), an annual household health survey administered by the US Census Bureau.

The results were published online in JAMA to coincide with their presentation.

The 34,426 adults who responded to the survey were asked if they had ever been told by a healthcare professional that their immune system was weakened, and whether that status still pertained.

Follow-up questions, designed to ensure the validity of the self-reported results, asked about medication use and diagnoses of cancer. Respondents whose answers appeared invalid, for various reasons, were excluded from the analysis.

"We generated national estimates of the prevalence of immunosuppression, taking into account the complex NHIS sampling design," Dr Harpaz explained.

Prevalence of Immunosuppression

Of the respondents included in the analysis, 1442 (4.2%) reported that they had been told by a healthcare professional at some point that their immune system was "weakened," and 951 (2.8%) reported current immunosuppression and additional evidence of immunosuppression.

The overall prevalence of immunosuppression was 2.7 per 100 Americans. It was highest in women, whites, and people aged 50 to 59 years.

Table. Characteristics of Respondents Reporting Current Immunosuppression

Respondent Characteristics Percent (n = 951) Prevalence per 100 Americans
White 67.4 3
Men 31.3 1.8
Age Range, Years
18 - 39 19.1 1.6
40 - 49 14.3 2.3
50 - 59 29.5 4.4
60 - 69 22.4 3.9
70 - 79 10.6 3.1
80+ 4.0 2.5
40 - 49 14.3 2.3
50 - 59 29.5 4.4

 

The higher prevalence among women might reflect a higher risk for autoimmune conditions. As expected, age-specific immunosuppression increased with age, in parallel with the epidemiology of prevalent conditions that require immunosuppressive treatments. However, it is not clear why it peaked in the 50- to 59-year age range, Dr Harpaz said.

A Growing Population

"There are hundreds of clinical trials underway assessing immunosuppressive treatments to prevent or mitigate chronic diseases in large-risk groups," said Dr Harpaz. "We are even seeing a phase 3 trial of an injectable interleukin-1-alpha inhibitor for the secondary prevention of myocardial infarction. If this pans out, consider how huge this population is."

"If the indications for immunosuppressive drugs are expanded to populations such as this — not to mention depression and aging, which I've also seen — this population could number in the tens of millions," he noted.

These results are a bit surprising, said Tanya Myers, PhD, a fellow in vaccinology training at the Emory University School of Medicine in Atlanta, Georgia.

"It's striking to me that there has not been a comprehensive assessment of this before," she said. What is also striking is "the number of treatments in development with the potential to further increase the population of immunosuppressed people.

 
For each of these populations of immunocompromised people, there has to be an assessment of the appropriate vaccination schedule. Dr Tanya Myers
 

"This has very real implications for me as an epidemiologist working on vaccine safety and for my field. For each of these populations of immunocompromised people, there has to be an assessment of the appropriate vaccination schedule," Dr Myers explained. "We need to decide if they are at risk and whether there are special populations that require other vaccine recommendations."

All healthcare providers should be aware of the trend and understand the impact on their own patient population, said Raymund Razonable, MD, professor of medicine at the Mayo Clinic in Rochester, Minnesota.

The findings fit with a trend he has observed in his own practice, he said, which is related to the increase in transplants and the use of biologics.

"These numbers," Dr Razonable predicted, "are definitely going to increase."

Dr Harpaz, Dr Myers, and Dr Razonable have disclosed no relevant financial relationships.

IDWeek 2016: Abstract 1439. Presented October 28, 2016.

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