Overlap in prevalence between various types of environmental intolerance

Environmental intolerance (El) is characterized by attribution of several, multisystem symptoms to specific environmental exposures, such as exposure to odorous/pungent chemicals, certain buildings, electromagnetic fields (EMFs) and everyday sounds. The symptoms are medically unexplained, nonspecific and the symptoms overlap between different types of El. To approach the issue of underlying mechanisms the matter of overlap in prevalence between intolerances can provide valuable information. The aim of the study was to examine if the overlap between intolerance to odorous/pungent chemicals, certain buildings, EMFs and sounds is larger than the expected overlap if no association would exist between them. The study was using cross-sectional data from the Vasterbotten Environmental Health Study in Sweden; a large questionnaire-based survey. 8520 adults (18-79 years) were randomly selected after stratification for age and sex, of whom 3406 (40%) participated. Individuals with the four types of intolerance were identified either through self-report, or by baying been physician-diagnosed with a specific EL The overlaps between the four EIs were greater than predictions based on coincidence for both self-reported and diagnosed cases (except for the overlap between diagnosed intolerance to sounds and EMFs). The results raise the question whether different types of El share similar underlying mechanisms, or at least that the sufferers of El share some predisposition to acquire the conditions. (C) 2013 Elsevier GmbH. All rights reserved.