Swedish Study Links Exposure to Silica Dust to Increased Risk of Sarcoidosis

Exposure to inhaled silica dust appears to increase the risk of sarcoidosis among men 20 to 65 years old, according to a recent study from Sweden.

Men 35 and younger, and older men with more than six years of regular exposure to the dust saw the highest risk.

The study, “Sarcoidosis and silica dust exposure among men in Sweden: a case–control study,” was published in the journal BMJ Open.

Sarcoidosis is an inflammatory disease that can significantly affect the lungs. Its root cause remains unclear, but many scientists believe exposure to environmental factors play a key role.

Silica dust, produced in masonry, mining, and glasswork, among other activities, has been proposed as one such factor, although few studies have investigated it. One of those studies, conducted by the authors of the current study, suggested that exposure to silica increases the risk of sarcoidosis in iron foundry workers.

The researchers now investigated further the possible link between silica exposure and sarcoidosis by comparing records in Sweden’s National Non-primary Outpatient Care Register to people’s occupations in the Swedish Occupational Register. Data from 2007 to 2016 were analyzed for individuals age 20 to 65 diagnosed with sarcoidosis.

Researchers selected 3,663 sarcoidosis cases and 7,326 controls (two controls per case, matched by age and sex), all of whom were men. The mean age of cases and controls was 44.7 years. Of note, the team found only 48 sarcoidosis cases among women, which proved too few for meaningful analysis so they were excluded from the study.

In total, 13.9% of men diagnosed with sarcoidosis had been exposed to silica dust in their occupation within the five years prior to diagnosis, compared to 11.3% of controls. This risk increased significantly in men diagnosed before turning 35 — 1.48 times greater risk.

“Exposure to respirable silica dust seems to result in an increased risk for developing sarcoidosis in men. For men of an age of 35 years or younger the correlation was statistically significant stronger than in older men,” researchers wrote.

For men older than 35 with exposure of more than 10 years to silica, the likelihood of developing sarcoidosis was 1.44 times higher.

Researchers found that two to 10 years of exposure to silica dust appeared to significantly raise the risk of sarcoidosis. Although this risk continued to rise with 11 years of exposure or more, such increase was not statistically significant.

“Exposure to respirable silica dust statistically significantly increase the [likelihood of developing] sarcoidosis, but neither the cumulative nor mean exposure show a statistical significant dose–response association,” the researchers wrote.

How silica dust might cause sarcoidosis remains unknown. The team suggested it could trigger an immune response in genetically predisposed people, noting that silica exposure is associated with autoimmune diseases such as rheumatoid arthritis, systemic lupus erythematosus, systemic scleroderma, and antineutrophil cytoplasmic antibody-related vasculitis.

Overall, the team concluded that “exposure to respirable silica dust increases the risk of sarcoidosis among men between 20 and 65 years of age,” and that “the risk seems to be higher among exposed men 35 years or younger and older men with longer exposure (more than 6 years).”

Further studies that take into account confounding factors such as smoking  are needed to confirm the findings, they stated.