Chloroform and Cognitive Function in the General Population of the US Elderly: A Cross-Sectional Study

Abstract Background Chloroform is a water disinfection by-product associated with hepatic, renal and neurotoxicity. High concentrations of chloroform are known to cause central nervous system depression; however, the association between blood chloroform levels and cognitive function in the general elderly population is unknown. In this study, we investigated the association between blood chloroform levels and cognitive function in the elderly US population (n=782). Methods We analyzed blood chloroform levels and cognitive function, as measured by the digit symbol substitution test (DSST), from the 2011-2012 and 2013-2014 National Health and Nutrition Examination Surveys (NHANES) for participants aged 60 years and older. Blood chloroform levels were measured using capillary gas chromatography and mass spectrometry with selected-ion monitoring detection and istotope-dilution. Results After adjusting for all covariates, increases in log-transformed blood chloroform levels were significantly associated with decreased DSST scores (β = -1.56, SE = 0.57, p-value 0.010). Compared with individuals in the lowest quartile of blood chloroform, the regression coefficients were significantly lower among those in the second and third tertile (tertile 2 β = -3.00 (SE = 1.25, p-value 0.022); tertile 3 β = -4.05 (SE = 1.22, p-value 0.002)). After stratification by obesity status, increases in log-transformed chloroform levels showed borderline significant associations with decreased DSST scores among the obese (β = -1.71, SE = 0.85, p-value 0.052). Conclusions Our finding suggest a possible link between blood chloroform levels and cognitive function in the US elderly population.