Sarcoidosis risk tied to current smoking, obesity, physical activity
Use of alcohol, smokeless tobacco products show no association in study
The risk of sarcoidosis is significantly reduced in people who smoke cigarettes and may be increased in people who are obese, a study in Sweden suggested.
While these findings are consistent with some previous studies, more research is needed to confirm them, the researchers noted in “Modifiable lifestyle risk factors for sarcoidosis: a nested case–control study,” which was published in ERJ Open Research.
A feature of sarcoidosis is the formation of atypical clumps of immune cells known as granulomas. It’s not known what causes the disease to develop and scientists are working to understand risk factors for it.
A team of scientists in Sweden analyzed data from a national study to identify modifiable lifestyle risk factors in sarcoidosis, meaning those people can theoretically change through lifestyle adjustments.
Obesity, smoking, alcohol, physical activity as risk factors
“Our aim was to investigate whether obesity, tobacco use, alcohol consumption and physical activity are associated with sarcoidosis risk among men and women in Northern Sweden,” the researchers wrote.
The study included data on 165 people (103 men, 62 women; median age 40) with sarcoidosis, as well as 660 age- and sex-matched people without the disease who served as controls. Both groups completed a self-administered questionnaire on demographics and lifestyle factors, and their physical measurements were collected.
Most sarcoidosis patients (88%) showed lung involvement.
The researchers used statistical models to compare lifestyle habits in the two groups.
Compared with controls, a higher proportion of patients were overweight (45.5% vs. 40.8%) and obese (14.5% vs. 11.3%), light drinkers (37.6% vs. 33.5%), former smokers (27.3% vs. 24.5%), and never-smokers (63% vs. 52.9%). A greater proportion of sarcoidosis patients were also physically active (24.8% vs. 19.7%).
After adjusting for potential influencing factors, the researchers found that obesity was associated with a 34% higher likelihood of having sarcoidosis compared with normal weight. Specifically, every one centimeter increase in waist circumference — generally indicative of a greater accumulation of fat around the abdomen — was associated with a 2% higher likelihood of sarcoidosis.
Increased odds of sarcoidosis were associated with the highest waist circumference categories in both men (by 24%) and women (by 42%).
None of these results reached statistical significance, however, meaning they could be due to chance.
Past, present smoking and sarcoidosis risk
Former smokers had a 33% higher chance of having sarcoidosis than those who never smoked, but this difference was also not statistically significant. The chance of having sarcoidosis was significantly lower in current smokers (by 52%) and in those who’d ever smoked (by 24%) compared with those who’d never smoked.
The researchers noted this apparently higher risk of sarcoidosis in former smokers might be explained in part by the fact that sarcoidosis often causes lung symptoms and patients may give up smoking in the disease’s early stages, even before they’re diagnosed.
Indeed, when the scientists excluded recently diagnosed patients from the analysis, there was no longer an association between former smoking and a higher sarcoidosis risk.
“However, the results with current smoking were not materially changed and cannot be explained by [early stage] sarcoidosis,” the researchers wrote, adding this raises the possibility that chemicals in cigarettes may be protective against developing sarcoidosis, noting an area for future exploration.
Those who were very physically active had a 25% higher likelihood of having sarcoidosis relative to those who were inactive, but this difference failed to reach statistical significance also.
“To our knowledge, this is the first study to investigate the relationship between physical activity and future sarcoidosis,” the researchers wrote, adding that a pro-inflammatory molecule profile of strenuous exercise is similar to the profile “that initiates and progresses the sarcoid granuloma formation and may play a role in sarcoidosis development.”
Using alcohol or snus, a Swedish smokeless tobacco product, were not significantly associated with sarcoidosis risk. Researchers speculated whether the lower risk seen with smoking indicates a “protective effect” or reflects early symptoms years before a diagnosis that affects a smoking habit. The researchers also said it’s not clear if the findings can be applied to other populations since all the participants were from northern Sweden, making more research needed.