Organic solvents and cognitive functioning. With special reference to interaction with aging

Abstract

The aim of the thesis was to study cognitive functioning in patients with chronic toxic encephalopathy (CTE) and in aging workers previously exposed to organic solvents. The discriminative power of a series of cognitive tests in identifying patients with CTE was examined. We also examined the influence of CTE on Trail Making Test (TMT) performance with special focus on the discrimina-tive potential of this test. Tests with high demands on perceptual speed and attention were most sensitive in distinguishing CTE patients from other patients as well as from healthy referents. Inferior TMT performance was seen in CTE patients, and increasing age had a negative effect on performance only for the CTE patients. The sensitivity of TMT alone was low, but the specificity was high. An 18-year follow-up study of floor layers, previously heavily exposed to solvent-based glues, and their controls (carpenters) examined cognitive performance in relation to baseline data. Tests of attention and memory, known to be sensitive to the influence of aging, were added to further explore the influence of past heavy exposure to organic solvents on cognitive functioning. The most exposed floor layers deteriorated significantly more over time in visual episodic memory and perceptual speed than their referents. Higher cumulative exposure was significantly associated with decrements in tests assessing visual episodic memory, perceptual speed, and visuospatial skill. The results suggest that the negative effects of exposure may interact with the normal aging process, primarily in the most heavily exposed individuals. Previous heavy exposure to solvent-based glues had a negative influence on cognitive functioning in domains known to be sensitive to the influence of aging, such as attention and episodic memory. Dose-effect relationships were seen mainly pertaining to contact adhesives. At moderate or high solvent exposure, the magnitude of the dose-related decrements, was comparable to between 10 and 25 years of aging, and was particularly pronounced in the memory tasks.