Catechol O-Methyltransferase (COMT) VAL158MET Functional Polymorphism, Dental Mercury Exposure, and Self-Reported Symptoms and Mood

Associations were evaluated between a functional single nucleotide polymorphism (Val158Met) in the gene encoding the catecholamine catabolic enzyme catechol O-methyltransferase (COMT), dental mercury exposure, and self-reported symptoms and mood among 183 male dentists and 213 female dental assistants. Self-reported symptoms, mood, and detailed work histories were obtained by computerized questionnaire. Spot urine samples were collected and analyzed for mercury concentrations to evaluate recent exposures, whereas a chronic mercury exposure index for all subjects was created from the work histories. COMT polymorphism status was determined using a polymerase chain reaction (PCR)-based assay. Scores for current, recent, and chronic self-reported symptom groups and six self-reported mood factors were evaluated with respect to recent and chronic mercury exposure and COMT polymorphism status. Multiple regression analysis controlled for age, socioeconomic status, tobacco and alcohol use, self-reported health problems, and medications. Separate evaluations were conducted for dentists and dental assistants. No consistent patterns of association between either urinary mercury concentration or the chronic index of mercury exposure and any category of symptoms were observed. However, consistent and significant associations were found between increased symptoms and the COMT polymorphism involving the double allelic substitution (full mutation) compared to subjects with no substitutions. Associations with mood were limited to polymorphism status among female dental assistants, and were observed for four of six mood factors and overall mood score. These findings extend evidence of genetic factors potentially affecting human susceptibility to the toxic effects of mercury and other environmental chemicals.