Researchers have conducted a trial of US residents aged 18 years or older using the 2013 National Health Interview Survey (NHIS), an annual health survey conducted via household interviews, to investigate the impact of immunosuppression on the population. The results showed that prevalence of immunosuppression was highest among women, whites, and persons aged 50 to 59 years.
The researchers carried out this investigation because the number of immunosuppressed adults in the US is unknown. The number is thought to be increasing because of both greater life expectancy among these adults due to improvements in medical technology and techniques, as well as new immunosuppressive treatments.
Immunosuppression means lowering the efficiency of a person’s immune system so it readily accepts an organ after a transplant. However, this also increases the risks and severity of primary or reactivation infections. It is also a threat to food and water safety, tuberculosis control, vaccine programs, infection control strategies, outbreak preparedness, travel medicine, and other vital public health sectors.
Immunosuppression may also occur due to malnutrition, naturally due to aging, immune-compromised diseases such as HIV and due to cancer. Suppressing the immune system for the purpose of organ transplant is usually done by drugs known as immunosuppressants.
In ideal situations immunosuppressants target only the most active part of the immune system and should not cause immunodeficiency. Such conditions can be particularly dangerous as it can mask the interaction of tumor cells with immune cells and might disrupt proper diagnosis and treatment.
In 2013, participants were asked if they had ever been told by a doctor or other medical professional that their immune system was weakened. If they answered yes, those participants were asked follow-up questions to assess whether that condition was current and to back their condition with additional evidence of immunosuppression.
Individuals who mentioned using immunosuppressive medications or treatments or occurrence of immunosuppressive medical conditions such as hematopoietic cancer or HIV infection were considered immunosuppressed by the scientists. Those reporting only frequent colds or infections or attributing immunosuppression to chronic diseases or to solid cancers were not considered to be immunosuppressed.
According to the results, it was estimated that 2.7% of US population were self-reportedly immunosuppressed. The study however did not investigate the actual causes behind individuals’ immunosuppression.
The scientists guessed that the factors could be accelerated by frequency and chronic conditions such as having a life-long immunosuppression due to HIV infection, seeking treatment for autoimmune conditions, or undergoing solid organ transplantation or undergoing short-term cancer chemotherapy.
The scientists further noted that there was a higher risk of immunosuppression in women which might point towards the biological differences between men and women that could factor as one of the causes that lead to immunosuppression.
Immunosuppression that was specific to age increased as individuals grew older, just like risk increased with medical conditions that require treatment via immunosuppressive techniques. The scientists are still clueless as to why it peaked specifically during the age bracket of 50 to 59 years.
The age specific and gender specific increase in immunosuppression prevalence might act as a hint for scientists who want to further explore the causes of immunosuppression and further studies might revolve around this discovery.
The study was far from perfect and had its fair share of limitations. The first being the obvious errors in self-reporting. Immunosuppression self-reports are prone to be wrongly classified, since there are so many interconnected intricate covariables that a non-medical person might not fully understand.
Since the spread of the results in the sensitivity analyses was small, it provides reassurance regarding the possibility of results being compromised due to misreporting.
With a limited number of survey questions, causes or subsets of immunosuppression could not be reliably determined. The scientists also had doubts whether data from the year 2013 would reflect the current incidences of immunosuppression. Moreover, the study excluded children and institutionalized adults, hence the scientists were restricted to studying only adults.
This study highlighted an overlooked condition which few researches had investigated before. It serves as a source of motivation for other scientists to amend the shortcomings of the current study and move it forward.
Tracking the progress of immunosuppression over time is now crucial than ever given the high number of clinical trials now underway to properly explore the efficacy of immunosuppressive treatments in preventing or curing common chronic diseases in individuals who are at a higher susceptibility of becoming diagnosed.