Introduction Exposures in the workplace may cause adult onset asthma. In this analysis, we present the prevalence of ever working in job categories and the associated risks of adult onset asthma by age 42 in participants in the 1958 birth cohort.

Methods All persons born in the first week of March in Britain in 1958 were recruited into the cohort. By age 42 9890 cohort members had provided a full occupational history and health information. Job titles and descriptions were initially coded into Standard Occupational Classification 1990 (SOC-90) using a text based computer program. Blind to asthma status we have recoded these jobs into the International Standard Classification of Occupations 1988 (ISCO-88) codes. The prevalence of ever working in jobs defined by these codes was determined. Adult onset asthma was defined as reporting ‘ever asthma’ at ages 33 or 42 and excluding all those who reporting ‘ever asthma’ at ages 11 or 16 (childhood asthma). The risk of adult onset asthma associated with these job categories was determined in logistic regression analysis adjusted for sex, smoking, region and father's social class at birth. The Simes procedure was used to correct for multiple testing.

Results After excluding childhood asthma the sample consisted of 8358 cohort members with a 9% prevalence of adult onset asthma. The most common jobs with the greatest risks of adult onset asthma are tabulated.

Conclusion Several job categories were associated with adult onset asthma by age 42 in this cohort of adults born in 1958. This analysis confirms in a British population existing knowledge about occupations associated with the development of asthma in working life, and in particular shows consistent evidence of asthma development in those who have ever worked as a cleaner.