Obesity is linked to an increased risk of sarcoidosis, while smoking was associated with a lower risk, according to a study reviewing medical records of nearly 350 patients.
Although the study, “Smoking, obesity and risk of sarcoidosis: A population-based nested case-control study,” published in the journal Respiratory Medicine, reflects findings reported in earlier studies, researchers emphasized that an association does not prove that smoking protects people from sarcoidosis.
Researchers at the Mayo Clinic in Rochester, Minnesota reviewed medical records of sarcoidosis patients in Olmsted County, Minnesota, to better understand whether obesity and smoking influenced the risk of the disease. The research team identified 345 cases that were diagnosed between January 1, 1976 and December 31, 2013.
As a comparison group, they used data from 345 people without sarcoidosis from the same population. To improve the analyses, the team matched each patient with a control of the same age and sex.
Before the analysis, researchers also made sure that patients had received a correct diagnosis by reviewing the medical charts and images taken during examinations.
Researchers extracted information about smoking at the time of diagnosis. This information is routinely gathered at the Mayo Clinic. The team also calculated the body mass index (BMI) from height and weight information in the records, and used data gathered within a year before or up to three months after the diagnosis.
The study showed that current smokers had a slightly lower risk of developing sarcoidosis compared to those who never smoked. Adding former smokers into the analysis did not change the result.
While overweight people did not have a higher risk of disease, those who were obese were about 2.5 times more likely to develop sarcoidosis than people with a normal or low BMI. When compared to the entire group of non-obese individuals, the risk was almost equally high. Also, taking smoking into account did not change the result.
Earlier studies have reported similar findings of a lower risk of sarcoidosis and certain other lung diseases in smokers. Researchers argued that this effect might have been brought on by a dampening effect on immune T-cells and macrophages by smoking.
“Current smokers have a lower risk of sarcoidosis while subjects with obesity have a higher risk of sarcoidosis in this population. Whether the associations are causal requires further investigation,” the team concluded in their study.