HELSINKI—Analysis of data from the Finnish national health insurance system reveals that occupational exposures account for more adult-onset asthma cases than had been estimated previously.[1]

Antti Karjalainen, MD, and colleagues examined applications for registration for asthma benefits among employed adult Finns (a total of 1.9 million workers) from a period of more than 12 years. The 49,575 incident asthma cases were categorized by profession, and relative risks were calculated for each job category with respect to incidence among clerical workers, who were assumed to have low occupational exposures.

Increased asthma risk was linked with specific industries, some previously unrecognized as occupational risks: agriculture, manufacturing, and service industries, such as cleaning and hairdressing. Results indicated that 29% of adult-onset asthma cases in men, and 17% of such cases in women, were attributable to occupation; previous Finnish estimates had suggested that only 6% of adult asthma cases in men and 4% in women were work-related. Therefore, occupational risk may be approximately fivefold greater than previously thought.

UNIDENTIFIED AGENTS MAY CONTRIBUTE TO ASTHMA

“The main reason for the discrepancy is that those cases of asthma caused by recognized sensitizing factors are a lot easier to diagnose than cases caused by nonspecific irritants,” said Dr. Karjalainen, a senior scientist at the Finnish Institute of Occupational Health in Helsinki. “We’ve already identified over 200 specific agents. But the majority of the problems may come from nonspecific irritants,” Dr. Karjalainen remarked. Despite the identification of particular substances encountered in the workplace as causes of asthma, the role of nonspecific respiratory irritants has been less studied and may contribute more than previously suspected, the authors argue.

FINNISH HEALTH CARE SYSTEM YIELDS WEALTH OF INFORMATION

Registration required of all those applying for asthma care benefits with the Finnish national health care system provided remarkably detailed data regarding the incidence of adult-onset asthma in relation to patient occupation. Because the sample included virtually all adult Finnish workers, the researchers were able to identify those occupations associated with excess asthma risk and, thus, to estimate the extent of occupation-related asthma not attributed to identified causes.

“Our study didn’t look at causes perse,” said Dr. Karjalainen, “but indirectly, you can draw conclusions about which occupations entail the greatest exposure to nonspecific irritants.” The statistics reflect “not only inception of asthma but also aggravation of existing, previously undiagnosed asthma,” he added.

STRATEGIES TO ADDRESS SUSPECTED OCCUPATIONAL ASTHMA

“Ask patients if they have factors at work—too little attention is paid to this,” recommended Dr. Karjalainen. “What I would do is to ask patients what they think is the most problematic [exposure] with regard to symptoms, then find out if there are any simple means to reducing the exposure.”

Apart from avoiding sources of such irritants, Dr. Karjalainen said there are few practical measures to limit occupational asthma caused by nonspecific irritants. “Masks would not be practical in many lines of work,” he told RESPIRATORY REVIEWS. “If there are several cases under similar circumstances, you might consult a national occupational health and safety expert for advice on how to reduce exposure.”

—Mimi Zucker, PhD