Effects of sarin on the nervous system in rescue team staff members and police officers 3 years after the Tokyo subway sarin attack.

Abstract

Although the clinical manifestations of acute sarin poisoning have been reported in detail, no comprehensive study of the chronic physical and psychiatric effects of acute sarin poisoning has been carried out. To clarify the chronic effects of sarin on the nervous system, a cross-sectional epidemiologic study was conducted 3 years after the Tokyo subway sarin attack. Subjects consisted of the rescue team staff members and police officers who had worked at the disaster site. Subjects consisted of 56 male exposed subjects and 52 referent subjects matched for age and occupation. A neurobehavioral test, stabilometry, and measurement of vibration perception thresholds were performed, as well as psychometric tests to assess traumatic stress symptoms. The exposed group performed less well in the backward digit span test than the referent group in a dose-effect manner. This result was the same after controlling for possible confounding factors and was independent of traumatic stress symptoms. In other tests of memory function, except for the Benton visual retention test (mean correct answers), effects related to exposure were also suggested, although they were not statistically significant. In contrast, the dose-effect relationships observed in the neurobehavioral tests (psychomotor function) were unclear. None of the stabilometry and vibration perception threshold parameters had any relation to exposure. Our findings suggest the chronic decline of memory function 2 years and 10 months to 3 years and 9 months after exposure to sarin in the Tokyo subway attack, and further study is needed.

Effects of Sarin on the Nervous System of Subway Workers Seven Years after the Tokyo Subway Sarin Attack

“…The exposed group also performed less well in the memory function tests though the differences were not statistically significant probably due to the small number of the subjects. These results were consistent with the previous study conducted 3 yr after sarin exposure 18) . The consistency of these findings suggests causal relationships between exposure to sarin and these disturbances.…”

“…In our previous study, 3 yr after sarin exposure, this point failed to show significance 18) . The prevalence distribution of digit numbers of the backward digit span test shifted dose-dependently as shown in the Figure. These results strengthen the case for causal relationships between sarin exposure and these effects.…”

“…In order to make the effects of sarin more evident with higher statistical power, the data of this study and a previous study 18) were combined together, and re-analyzed. The number of the combined study subjects was 80 exposed subjects, consisting of 30 high-exposure and 50 lowexposure subjects, and 65 referents (Table 1).…”

“…Computerized neurobehavioral tests for psychomotor and memory function and stabilometry were performed using the same methods, apparatus and procedure as in the previous study 18) to evaluate the chronic effects of sarin on the nervous system. Briefly, finger tapping interval (dominant and non-dominant hands), simple reaction time and choice reaction time were measured for assessing psychomotor function, digit span (forward and backward) and the Benton visual memory retention test (BNT) were selected for checking memory function, and body sway was examined using a strain-gauge type force platform (Gravicorder GS-3000; ANIMA, Tokyo, Japan), first with the subjects' eyes open, then with their eyes closed for 60 s. In BNT, only the latter 5 geometric patterns out of the 10 original patterns were examined because the first 5 patterns are too simple for assessing short-term memory of healthy adults.…”

“…Though cholinesterase activity is known to recover to normal levels in approximately 3 months 17) , these studies suggested the existence of chronic effects due to sarin. In 1998, we performed a cross-sectional study concerning effects of sarin on the nervous system in rescue staff and police officers 3 yr after the Tokyo subway sarin attack, and reported a decline in memory function 18) , but we failed to show a significant tapping time elongation, though a tendency was found. In 2002, 7 yr after the attack, we had the opportunity to investigate 26 sarin exposed and 13 referent subway workers of the Teito Rapid Transit Authority.…”