Scientists are working diligently to find the cause of sarcoidosis, but the answer is still unclear. They have uncovered evidence that suggests certain genetic and environmental factors are involved, but with so many factors coming into play, it is difficult to tell what is really having an effect. Many scientists believe that smoking is linked to sarcoidosis in some way – however, there is disagreement in the community about whether smoking is positively or negatively correlated with sarcoidosis development. Several studies have been conducted, all of which have yielded varying results. A recent study published in Scientific Reports sought to remove some of the variables that may have influenced the data in other studies, allowing the researchers to best observe the effects that smoking has on the development of sarcoidosis. In order to accomplish this, researchers conducted a study in which the genetic information of all participants was taken into account. To do this, they conducted a population-based case-control study by employing a gene-environment interaction approach.
What is a Case-Control Study?
A case-control study compares patients who have a certain illness with patients who do not have that illness. During the study, a risk factor is observed within both experimental groups, and researchers compare how frequently the exposure to that risk factor affects the people in each group. This data is meant to help researchers determine the relationship between the risk factor and the disease. In this type of study, there is no intervention from the researchers. Therefore, a case-control study is purely observational and intended to estimate probability.
What is a Gene-Environment Interaction Approach?
In order to discover if a certain gene and a certain environmental factor each have an independent effect on the development of a disease, scientists must observe the interaction of these factors individually. The best way to do this is by observing whether or not these factors maintain the same effects when they are both influenced by a third factor. If not, then scientists can assume that these factors are influencing each other to some degree. In this study, researchers sought to discover how smoking affects sarcoidosis patients by separately observing the effects of smoking on both patients with and without Lofgren’s Syndrome, as well as patients that both do and do not exhibit the HLA-DRB1*03 allele, which is believed to have a separate significant impact on sarcoidosis development.
Results
The results of our study showed that smoking modulates disease risk by 56% in LS and 62% in non-LS if patients have both risk factors; that is, the risk allele and smoking, and henceforth offering new insights on the disease susceptibility and its interaction to smoking exposure.
What this means is that smoking does increase a person’s chances of developing sarcoidosis, but only if he or she is already genetically susceptible. By isolating the variables in question, the researchers were able to determine the circumstances under which smoking creates a higher risk of sarcoidosis. According to the study, the HLA-DRB1*03 allele and the habitual act of smoking must both be present in order for smoking to increase the risk of a person developing sarcoidosis. This is important information for the sarcoidosis community because it advances our knowledge of what causes sarcoidosis. It can be assumed that there are both genetic and environmental factors that increase a person’s risk for sarcoidosis, and often times, these factors must go hand-in-hand.
Sources:
https://www.nature.com/articles/s41598-019-54612-1
https://himmelfarb.gwu.edu/tutorials/studydesign101/casecontrols.cfm
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2823480/