Abstract
The purpose of the present study was to compare specific neuropsychological, psychological, and family history patterns, as well as cardiovascular reactivity of three community-recruited groups of nonsmoking, nonalcoholic middle-aged individuals with and without the symptom of intolerance to low levels of environmental chemicals (CI). CI is a common symptom in chronic fatigue syndrome and fibro-myalgia. The groups included: (i) CI who had made associated lifestyle changes because of the CI (CI/LSC); (ii) CI who had not made such changes (CI); and (iii) normals without CI (N). All subjects underwent an evaluation session followed by two laboratory cognitive and psycho-physiological test sessions one week apart. The CI/LSC diverged from the other groups in exhibiting poorer performance on the Continuous Visual Memory Test (CVMT) in terms of more false alarms and fewer correct hits, but normal performance on a visuospatial test of divided attention (DAT). In contrast, the CI group showed progressively poorer performance on the DAT with practice, but were like the N on the CVMT. The CI group showed a complex sensitization (amplification) of heart rate response to the DAT over time. In addition, the CI/LSC had the highest rate of family histories of alcohol problems and of attention deficit disorder, as well as of antihypertensive medication treatment and self-reported past emotional/physical abuse. Taken together, the data suggest that individuals with CI comprise a heterogeneous population requiring careful definition of subtypes for future studies.