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Introduction: Attention-Deficit/Hyperactivity Disorder (ADHD) is a recognized neurodevelopmental disorder with a complex, multifactorial origin. Lead (Pb) and mercury (Hg) are highly toxic substances that can potentially impair brain development and have been implicated in the development of ADHD. This systematic review aims to analyze the epidemiological literature regarding the association between Pb and Hg exposure and the diagnosis of ADHD., Methods: From November 1983 to June 2, 2023, a comprehensive search was conducted in multiple databases and search engines, including PubMed, Web of Science, Scopus, and Google Scholar. Observational studies (case-control, cohort, and cross-sectional) measuring Pb and Hg levels in various biological samples (blood, hair, urine, nail, saliva, teeth, and bone) of children with ADHD or their parents and their association with ADHD symptoms were included., Results: Out of 2059 studies, 87 met the inclusion criteria and were included in this systematic review. Approximately two-thirds of the 74 studies investigating Pb levels in different biological samples reported associations with at least one subtype of ADHD. However, most studies examining Hg levels in various biological samples found no significant association with any ADHD subtype, although there were variations in exposure periods and diagnostic criteria., Conclusion: The evidence gathered from the included studies supports an association between Pb exposure and the diagnosis of ADHD, while no significant association was found with Hg exposure. Importantly, even low levels of Pb were found to elevate the risk of ADHD. Further research is needed to explore the comprehensive range of risk factors for ADHD in children, considering its significance as a neurodevelopmental disorder., (© 2024. The Author(s).)

Lead is a common toxin which has detrimental effects on human health. Since lead poisoning is not associated with specific symptoms, diagnosing elevated blood lead concentration (EBLC) should be taken seriously. The purpose of this study was to propose a prediction model for EBLC based on demographic and clinical variables through a decision-tree model.In this cross-sectional study, 630 subjects (above 40 years old) living in South Khorasan Province, Iran in 2017 were selected via cluster random sampling method. From among the 630 participants who met the inclusion criteria, 70% ( N  = 456) were chosen randomly to achieve a set for developing the decision tree and multiple logistic regression (MLR). The other 30% ( N  = 174) were placed in a holdout sample to examine the function of the decision tree and MLR models. The predictive performance for various models was studied using the Receiver Operating Characteristic (ROC) curve.In the decision tree model, the parameters of hematocrit (HCT), White Blood Cell (WBC), Red Blood Cell (RBC), Mean corpuscular volume (MCV), creatinine concentration, abdominal pain, gender, route of administration, and history of cigarette smoking were the most critical factors in identifying people at risk of EBLC. The HCT concentration was the most critical variable, which was chosen as the root node of the tree. Based on the ROC curve, the decision tree model had better predictive accuracy than the logistic regression model.Our results indicated that the decision tree model offers far greater predictive precision than the logistic regression model. Doctors should pay more attention to some factors including the hematological parameters such as MCV, RBC, HCT, leukocytosis, creatinine levels, male sex, history of cigarette, and opium consumption for the screening of EBLCs.

Background: Lead is a toxic metal that affects almost every organ in the body. Children are more susceptible to lead toxicity because they ingest non-food items (pica), have oral exploratory habits, absorb more substantial amounts of ingested lead compared to adults, and have a developing central nervous system. This study describes venous blood lead concentrations (BLC) in young children living in Birjand, Iran., Methods: A cross-sectional study was performed in 2016 on children 1-7 years of age who were referred to healthcare centers in Birjand City. Demographic information was obtained, and their BLC was tested using atomic absorption spectrometry (AAS)., Results: Four hundred children were tested. Their mean age was 52.37 ± 23.77 months; their mean BLC was 2.49 ± 2.64 μg/dL (median 1.85 μg/dL). Thirty-two (8%) children had a BLC > 5 μg/dL. A logistic regression model revealed that per one unit of increase in age, the chance of an elevated BLC decreased by 3% (OR (95%CI): 0.97 (0.96-0.99), p < 0.01). The risks of an elevated BLC was 61% lower in girls compared to boys (OR (95%CI): 0.39 (0.17-0.92), p = 0.03). Further, per one rate of increase in the BMI, the chance of an elevated BLC was higher (OR (95%CI): 1.13 (1.02-1.24), p = 0.01). Children whose fathers were laborers had higher BLC than those with employee fathers (p = 0.01)., Conclusion: Of 400 children aged 1-7 years old living in Birjand, Iran, 8% had elevated BLC. BLC correlated with the child 's age, gender, body mass index, and father's occupation.

Objectives: This exploratory investigation aimed to measure blood lead levels and associated risk factors in exposed workers in Iran, and to derive appropriate reference values for blood lead in this population as a means of epidemiological comparison., Design: Cross-sectional., Setting: Manufacturing plants with potential lead exposure in Southern Khorasan Province, Iran., Participants: The study included 630 workers, selected through stratified random sampling., Primary and Secondary Outcome Measures: The primary measures in this exploratory investigation were venous blood lead concentration (BLC) and associated risk factors of age, gender, work experience, cigarette smoking and history of opium use. The secondary measures were symptoms associated with lead toxicity. Data analyses were conducted using Student's t-test, Mann-Whitney U test, one-way analysis of variance, Kruskal-Wallis test, Spearman correlation coefficient and regression analysis., Results: Mean and median BLCs were 6.5±8.1 μg/dL and 3.9 μg/dL (IQR: 2.9-5.8), respectively. Of the subjects, 85 (13.5%) had BLC ≥10 μg/dL. The derived reference BLC value in this study was 30 μg/dL for men and 14 μg/dL for women. Increasing work experience and age were associated with BLC >10 μg/dL. Radiator manufacturers were up to 12.9 times (95% CI 4.6 to 35, p<0.005) more likely than painters to have BLC >10 μg/dL. Most subjects reported multiple symptoms., Conclusions: The mean BLC was above the maximum recommended concentration. There was a significant relationship between higher BLC and age or working in a printing factory or radiator manufacturing. These findings can direct efforts towards reducing occupational lead exposure., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2019. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: Multiple sclerosis (MS) is a debilitating disease of the central nervous system, with disseminating demyelination of nerve fibers and spinal cord. Exposure to heavy metals seems to be associated with a higher incidence of MS. Few studies have assessed the correlation of the incidence of MS with heavy metal concentrations. The present study aimed to assess the relationship between blood lead levels and MS., Methods: This case-control study was conducted on 29 MS patients and 29 healthy control persons. The controls were age, gender and occupation matched at the time of blood sampling. Blood lead levels were measured using the atomic absorption spectrometry method. Data were analyzed using Student t-test, Mann-Whitney U, and multiple logistic regression, using a significance level of p ˂ 0.05., Results: According to the result of this study, the mean blood lead level (BLL) was 75.6 ± 9.35and33.8 ± 28.8 µg/L in patients with MS and control group, respectively. Median blood lead levels were significantly higher in MS patients (38 µg/L, range: 27-67), compared to the controls (30 µg/L, range: 11-49) (p = 0.03). The risk of MS increased 1.17 times per one µg/L increment of blood lead level, using the multiple logistic regression analysis on the present results., Conclusion: In conclusion, based on our results, BLL was higher in MS patients, compared with healthy individuals. The risk of MS increased 1.17 times per one µg/L increment of blood lead level., (Copyright © 2018 Elsevier B.V. All rights reserved.)

The aim of this study to the estimate the lead concentrations in the blood of the adult population in South Khorasan Province, evaluate factors related to high lead blood concentrations and establish lead reference values (RVs) in our study population. In cross-sectional study, 400 people who lived in the province of South Khorasan in 2017 were selected. Demographic information was collected and clinical examinations were performed. As the geometric means, blood lead concentration (BLC) was expressed, 10th, 50th, 90th, and 95th percentiles, and 95% confidence intervals (CI) of the 95th percentile. The upper limits rounded values of the 95% CI with the 95th percentile were applied to calculate RVs. Mean BLC was 6.02 ± 7.41 µg dL -1 , median of BLC was 4.4 µg dL -1 (IQR: 2.9-6.5; range 0.9-54.7 µg dL -1 ). One hundred and twenty-five (31.2%) participants had BLCs between 5 and 10.0 µg dL -1 , 40 (10.0%) between 10 and 20.0 µg dL -1 , and 15 (3.8%%) over 20 µg dL -1 . The RVs for BLC for men and women were 16 [95% CI: 10.13-15.96] µg dL -1 and 15 [95% CI: 9.81-14.45] µg dL -1 , respectively. Higher BLCs were significantly associated with age, gender, hemoglobin, white blood cell count, and serum phosphorus concentration. This bio-monitoring study of BLCs in the general population of South Khorasan Province offers important demographic and lifestyle factors-stratified reference data. It is essential to continue efforts to reduce lead exposure.

Background: It is argued that breakdown of β-amyloid in the brain causes deposition of senescent plaques and therefore Alzheimer's disease (AD). One of the influential factors for increasing level of this protein is exposure to lead. Our aim was to compare blood lead levels (BLLs) between patients with AD and healthy controls., Methods: This case-control study was performed on all patients with cognitive impairment who were referred to the Neurological Clinic of Birjand in 2016 to 2017. Patients were referred to the laboratory for measurement of their serum levels of lead. The controls and patients were matched by age and sex., Results: In the AD case group, the average BLL was 22.22 ± 28.57 μg/dL. Mann-Whitney U test showed that BLLs were significantly higher in the patients than in the controls. The unadjusted odds ratio for BLL among the patients was 1.05 (95% confidence interval: 1.01-1.09; P = .01) compared to the controls., Conclusion: In the present study, BLL was associated with AD.