Introduction:
Occupational asthma (OA) is the most common occupational lung disease in industrialized countries; however, in Western Europe, a decline in the prevalence of OA and changes in etiological factors has been recorded. Data from Central Europe, where in the past healthcare and economy sectors were different, are rare.

Objective:
The aim of this study was to discover the changes related to OA during a four decade long period in the Slovak Republic.

Material and methods:
The study included patients whom OA was reported during 1980–2016. All cases of OA were divided into four decades. The prevalence of OA, changes in etiological factors and key diagnostic methods were evaluated. All decades were analysed separately and compared to one another.

Results:
During 1980–2016, OA was reported in 155 patients. OA was most often found in the second decade (6.4 cases per year), the lowest number of cases was diagnosed in the third decade (2.1 cases per year). Since 1988, an increasing prevalence of OA was observed with the peak in 1992, followed by the significantly progressive decrease during subsequent years. In the fourth decade, a mild increase in OA causes was recorded again. In the first and second decades, agricultural allergens were the dominant agents, which were replaced by chemical factors in the last decade. The most frequently used key diagnostic methods in 1980–2009 were skin tests, during the fourth decade the importance of this method declined. However, specific BPT a serial BPT were more frequently used in the fourth decade

Conclusion:
The number of OA cases induced by agricultural allergens declined, which was connected with a decrease of total OA cases. The current problem is the OA induced by the chemicals, which increased significantly in the last decade, even the possibility of underdiagnosed OA cases still exists.