Exposure to respirable crystalline silica in sand, rock or soil also is associated with lung fibrosis and increased RA risk. Findings from the EIRA population study showed that men who work in professions where they have high exposure to silica, such as drilling or crushing stone, had double the RA risk of men with lower exposure.5 Prevalence is as much as five times higher among men who work in such settings and also smoke, Dr. Symmons said.
Diet’s Role
Obesity is a known risk factor for developing RA, because adipocytes are not inert, but produce adipokines, cytokines, chemokines and other pro-inflammatory proteins and hormones, said Dr. Symmons. Data from the Mayo Clinic study suggest that recent increases in prevalence of RA may be due to simultaneous increases in obesity among Americans, she said.
Obesity increases RA risk in women who are either ACPA seropositive or seronegative according to the Nurses’ Health Study data, but other data show it may be somewhat protective for men.6 The Swedish EIRA study showed that obesity in men was associated with a decreased risk for seropositive RA, but not in women.
Sugar-sweetened beverages, such as soft drinks, may be associated with higher RA risk in women according to recent prospective studies, she said. Consumption of these drinks may also be a factor in obesity.
Does vitamin D intake through sunlight exposure or diet also serve as a protective factor for RA? Data from the Nurses’ Health Study suggest that levels of ultraviolet B light exposure may be related to RA risk in women, said Dr. Symmons. The connection is still inconclusive based on the available evidence, so potential interventions with dietary supplementation of vitamin D or increased UVB exposure are a long way off.
“Even with regard to RA prevention, one can only say that if a susceptible person is found to be vitamin D deficient, then advising more sunlight exposure and so restoring vitamin D levels may be helpful, although there is no evidence to support this approach. It’s just a conclusion from the risk factor data,” she said. Some research shows that obese participants have lower vitamin D levels than non-obese ones, and also typically exercise less, so RA risk may be due to a mixture of factors, she said.
Other modifiable dietary risk factors could either help trigger RA or offer some protection. “You’ll be pleased to know that alcohol is not a risk factor for rheumatoid arthritis,” Dr. Symmons told the audience. According to the Nurses’ Health Study data, daily intake of less than 10 g of alcohol a day offered some protection, while higher intake offered no protection, so only mild consumption is helpful.
