Microbial exposure in childhood linked to sarcoidosis in adulthood
Japanese study finds attending nursery school, using well water increase risk
Higher, daily exposure to microorganisms during childhood is significantly associated with an increased chance of developing sarcoidosis in adulthood, according to a study in Japan. Among the risk factors identified are attending nursing school and using well water.
A smoking history during adulthood was also significantly linked to a higher risk of sarcoidosis, as was a history of tuberculosis infection, the data show. In contrast, being breastfed was found to be a protective factor against the inflammatory disease.
“Both adulthood lifestyle history and childhood hygiene environment were associated with sarcoidosis,” researchers wrote. “Daily direct exposure to diverse microorganisms during childhood may increase the likelihood of [microbial triggers] for granuloma formation entering the body and also modify susceptibility to sarcoidosis.”
The study, “The hygiene environment during childhood may affect susceptibility to sarcoidosis: A case-control study of environmental risk factors,” was published in Respiratory Investigation.
Risk higher for rural residents, farm families, pet owners
Sarcoidosis is marked by small clumps of immune cells, called granulomas, that can accumulate in virtually any body tissue or organ, but most commonly the lungs. Over time, granulomas can harden and cause permanent damage.
The exact cause of sarcoidosis is unknown, but the disease typically begins with a triggering event, such as an allergic reaction or an infection. Some evidence suggests exposure to certain environmental factors can increase the risk of developing sarcoidosis. These include soil, dust, mold, tree pollen, and insecticides.
“However, evidence of the involvement of environmental factors in the [development] of sarcoidosis remains insufficient,” wrote researchers in Japan who investigated the link between various environmental exposures and sarcoidosis risk.
“Because residents in Japan have a relatively [similar] racial composition with common genetic factors to some extent, we presumed that, in comparison with studies in Western countries, we could focus more on differences in environmental factors,” the team wrote.
The study included 164 adults with sarcoidosis, 61% of whom were women, and 1,779 residence-matched people, who served as controls. Participants completed a questionnaire on childhood environment, adulthood lifestyle, and a history of infection.
Regarding childhood exposures, the risk of developing sarcoidosis in adulthood tended to be higher for those who were delivered via vaginal birth, attended nursery school, and had siblings living in the same house.
Other childhood risk factors that implied microbial exposure included the use of antimicrobial medications at least four times per year, living in a rural area, using well water, residing near agricultural fields, being part of a farming family, rearing livestock, and keeping pets.
These factors cause “abundant and diverse microbial exposure during early childhood, potentially influencing the immune response in adulthood,” the researchers wrote.
More sarcoidosis patients had history of hepatitis C, tuberculosis
In comparison, the risk of sarcoidosis tended to be lower for those who were breastfed, lived in a commercial area, and had access to a sewage system, “which are factors that enhance lifelong immunity against microorganisms or reduce microbial exposure during childhood,” the team wrote.
When the researchers examined adulthood lifestyle, significantly more sarcoidosis patients were either current or former smokers than controls (49.4% vs. 33.5%). There was also a trend toward a higher frequency of sarcoidosis in adults who kept pets and a lower frequency among those who spent at least one hour outside per day.
In terms of history of infection, more sarcoidosis patients had a history of hepatitis C infection (2.8% vs. 0.9%) and tuberculosis (2.8% vs. 0.9%) than controls.
Statistical analyses adjusted for potential influencing factors showed attending nursery school and exposure to well water between birth and 2 years of age each nearly tripled the risk of sarcoidosis in adulthood. Likewise, use of well water between the ages of 3 and 6 also nearly tripled the risk of sarcoidosis.
This study suggests that environmental risk factors, particularly the childhood hygiene environment, may affect susceptibility to sarcoidosis.
A history of tuberculosis infection showed the strongest link with sarcoidosis, boosting its risk by nearly six times. In contrast, breastfed children showed a 64% reduced risk of sarcoidosis as adults.
It’s possible “sarcoidosis and tuberculosis share a common factor that causes susceptibility to granulomatous diseases,” the researchers wrote. “Individuals with a history of tuberculosis frequently undergo chest X-rays, which may facilitate the detection of sarcoidosis.”
In addition, a smoking history in adulthood more than doubled the risk of developing sarcoidosis.
“This study suggests that environmental risk factors, particularly the childhood hygiene environment, may affect susceptibility to sarcoidosis,” the researchers wrote.
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