The study also shows that cleaners have 40 per cent higher risk of developing asthma than others.
The research includes 6 000 participants, based on the European Community Respiratory Health Survey (ECRHS).
The study is published by the American Journal of Respiratory and Critical Care Medicine, and is part of the Horizon 2020 project Aging Lungs in European Cohorts (ALEC).
Read more at the University of Bergen web page