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Coal mining linked to 33% of RA cases in Appalachia
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One-third of rheumatoid arthritis cases in Appalachia — as well as 20% of arthritis diagnoses overall — among men aged 50 years and older are attributable to coal mining work, according to recent data in Arthritis Care & Research.
“Multiple independent studies have found that occupational exposure to mineral dust is strongly associated with rheumatologic disease risk,” Gabriela Schmajuk, MD, of the University of California, San Francisco, and colleagues wrote. “Rheumatoid arthritis has been the condition most strongly implicated in mineral dust inhalation. The role that coal and silica dust inhalation may play in the colocation of U.S. regions in which coal mining is concentrated and where there is a high prevalence of arthritis in males is not clear.”
To analyze the link between RA and work-related exposure to coal and silica in mining regions, Schmajuk and colleague conducted a random-digit-dial telephone survey in selected counties in Appalachia. The researchers limited their research to English-speaking men aged 50 years and older with any employment history, living in mining regions of Kentucky, Ohio, Pennsylvania, Tennessee, Virginia and West Virginia, where workers demonstrated higher levels of pneumoconiosis mortality.
The 10-minute telephone interviews assessed employment, smoking history and sociodemographic information, as well as arthritis diagnoses and treatment. The researchers made 30,448 call attempts, making 7,710 contacts with potential participants, of whom 3,704 were excluded for age, sex, language or residence. An additional 3,003 refused to participate, while 30 reported no work history, leaving a total sample size of 973 participants. The researchers used multivariable logistic regression analysis to calculate odds ratios and associated population attributable fraction estimates.
According to the researchers, 27% of the included participants reported a history of coal mining work, with 19% stating they had other work-related silica exposure. In addition, 53% said they had been diagnosed with any arthritis, with 12% meeting the criteria for RA. After adjusting for covariates, the Schmajuk and colleagues found that coal mining was associated with a higher likelihood of RA (OR = 3.6; 95% CI, 2.1-6.2), with a population attributable fraction estimate of 33% (95% CI, 26-40).
Coal mining work was also associated with elevated levels of any arthritis (OR = 2.3; 95% CI, 1.6-3.2), with a population attributable fraction estimate of 20% (95% CI, 14-25).
“Our findings of increased odds ratios for arthritis and RA among coal miners in Appalachia are robust, unlikely explained by biased reporting or confounding, and are consistent with other studies, primarily of silica exposure outside of coal mining,” Schmajuk and colleagues wrote.
“Given that treatment guidelines for RA indicate that a disease-modifying agent should be initiated soon after onset of disease, earlier disease detection could be achieved through targeted surveillance among current and former coal miners,” they added. “However, the results reported here suggest that primary prevention of arthritis due to workplace protections for dust inhalation may reduce the prevalence of arthritis in general and RA in particular in the first place.” – by Jason Laday
Disclosure: Schmajuk reports no relevant financial disclosures. Please see the study for all other relevant financial disclosures.
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Eileen McCullagh, BSN, RN, ONC, CCRC
In their population-based survey of men aged 50 and older living in Appalachia, an area with historically high mortality rates from coal works pneumoconiosis, Schmajuk and colleagues examined whether coal mining is the connection between the prevalence of arthritis, especially rheumatoid disease.
The results of this study demonstrated that one in two males over the age of 50 reported arthritis and more than one in 10 met their case definition of RA. Occupational exposure to silica or being a coal miner occurred in 47 % of the respondents. Since silica exposure was common in these men and the odds of developing RA increased in association with such exposure, the researchers estimated that one-third of the cases of RA were attributable to coal and silica exposure
Few studies have examined the prevalence of RA among U.S. coal miners, and those studies that were done often involved radiographic and serologic data which this study did not have. The researchers admitted limitations, namely that their definition of RA was conservative based on the respondent’s report of a health care provider’s diagnosis and self-reported glucocorticoid use, which can lead to reporting bias and might lead to persons with coal mining histories more likely to report disease thus leading to a false association.
Findings obtained from this study are important in this growing body of knowledge on coal and silica dust among coal miners in this underserved region of the country. Further study is necessary to assist in allocating the much-needed funds to assist with workplace protection for dust inhalation and, hopefully, reduce the prevalence of arthritis and RA in this population.
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