CANADA-Occupational asthma (OA) may play a more significant role in the development of adult-onset asthma than has been previously recognized, a recent study demonstrates.[1]

Anthony R. Johnson, MD, et al conducted a population-based, cross-sectional study between March 1993 and November 1994 of adults in six Canadian communities: five urban areas (Vancouver, British Columbia; Winnipeg, Manitoba; Halifax, Nova Scotia; Hamilton, Ontario; and Montreal) and one mixed urban/rural setting (Prince Edward Island).

Initially, 18,701 people, ages 20 to 44 years, completed screening questionnaires. Of these, 2,974 agreed to undergo additional laboratory testing. Asthma was diagnosed in 383 of the 2,974 patients; in 166 cases, the asthma had developed during adulthood (ie, the first asthma attack had occurred at age 15 or older).

The authors divided the cases of OA into two categories: probable and possible. Study participants met the criterion for probable OA if their first attack coincided with their employment in an occupation and industry thought to carry a high risk for asthma. Participants were considered to have possible OA if they had a history of both asthma and occupational exposure to a causative agent but did not report working in a high-risk occupation and industry.

Of the 166 patients with adult-onset asthma, 27 had probable OA. Thirty-three people met the criterion for possible OA.

The two groups were similar in terms of their clinical characteristics, and they reported similar types of exposures at the onset of their asthma attacks. In most cases, the suspected etiologic agent was a high-molecular-weight substance, such as latex, grain, or a biologic enzyme. Among the patients with probable OA, the most common occupations were nursing; baking; chemical, rubber, and plastics processing; and hairdressing. In the possible OA group, the most common occupations were clerical work and food preparation.

The authors emphasize that the results of their study underscore the importance of not only ascertaining the occupation of the patient with new adult-onset asthma but also exploring the causative agents with which the patient may have come in contact.

“... One in three cases of adult-onset asthma may have been caused by occupational exposures,” Johnson et al conclude. Further, “18% of adult-onset asthma [cases] may be prevented by eliminating exposure to known occupational inducing/sensitizing agents.” They add, “Occupational exposure as a cause of adult-onset asthma may be more common than is realized.”

--Jennifer A. McConnon