Neurological Changes of Adults Residing in Lead Exposed Environment of Myeik Township

Abstract

Lead crosses blood brain barrier and adversely affects the cognitive function, causing impairment of neuropsychological functions. Most of the lead poisonings are asymptomatic and subclinical cases. A cross-sectional analytical study was designed to assess the neurological changes of adults, aged between 20 to 45 years old, residing in lead exposed environment of Myeik Township. The study focused on the cognitive and psychomotor ability of people who lived in those areas at least one year. A total of 95 subjects were interviewed by using the structured questionnaires for assessment of cognitive and psychomotor ability by well-trained researchers. The mean age of all participants was 32.7±8.5 years. The average duration of stay in these areas was approximately 20 years (maximum duration=47 years). The blood lead level was measured by graphite furnace Atomic Absorption Spectrophotometer. The mean blood lead level of all participants was 19.91±1.8 µg/dl. All the participants were divided into two groups: lower blood lead group (blood lead <10 µg/dl) (n=37) and higher blood lead group (blood lead ≥10 µg/dl) (n=58). The cognitive function was assessed by using three subtests (digit span, visual memory and paired associate learning) from the General Memory Scale. The mean scores were (10.51± 2.0, 5.59±0.5 and 20.01±8.3) in lower blood lead and (9.55±1.8, 5.12±0.7 and 15.23±5.2) in higher lead group, respectively. In addition, the mean total score of cognitive ability test in lower blood lead group was (36.12±9.5) and higher group was (29.90±5.8). All 3 test scores and total scores were significantly lower in higher blood lead group and it could be concluded that the higher the blood lead level, the lower the cognitive ability. To assess psychomotor ability, we used digit symbol, Bourdon-Wiersma vigilance tests and Santa-Ana dexterity test. Among these three tests, the mean scores of Santa-Ana dexterity test (dominant hand) was significantly longer duration (54.40±10.9 vs. 59.46±10.18) in higher blood lead group than in lower blood lead group. All these findings pointed out that lead intoxication would reduce not only cognitive ability but also psychomotor ability