Effects of acute organophosphate ingestion on cognitive function, assessed with the mini mental state examination

Chronic damage to the central nervous system resulting in cognitive impairment has been shown with repeated, low doses of organophosphorus (OP) exposure over month or years.

The study aimed to find out whether there is any cognitive impairment following acute OP exposure that could be detected by a simple screening instrument, the Mini Mental State Examination (MMSE), in clinical settings.

A cohort study.

The study was conducted with matched controls. Consecutive patients admitted to the hospital with acute ingestion of OP were recruited. Cognitive function was assessed with the MMSE, digit span test, test of long-term memory function and concentration. Patients were assessed twice: at 1 and 6 weeks of exposure.

Continuous variables were analyzed with the paired and unpaired T-tests. Non-normally distributed data were analyzed with the Mann-Whitney U test and Wilcoxon Signed Rank test. Discrete variables were analyzed with the Chi-square test.

There were 60 patients and 61 controls. The mean age (SD) of the patients and controls was 31.5 (11.6) and 31.3 (11.8) years, respectively. Forty-two patients turned up for the second assessment. Significant impairment of cognitive function was seen in the total score of MMSE (95% CI -2.5 to -0.3), orientation (95% CI -1 to -0.2) and language (95% CI -0.9 to -0.1) domains of MMSE, digit span test (95% CI 0.1-1.7) and test of long-term memory function (95% CI 0.3-2.3) in the first assessment compared with the controls. When the results of the second assessment were compared with the controls, no significant differences were seen.

Although there was a slight transient cognitive impairment detected with the screening tests following acute OP ingestion, no long-term cognitive defects was detected.