Association of blood lead level with cognitive performance and general intelligence of urban school children in ten cities of India

Background: Lead is toxic to children and effects the cognitive development. The primary objective was to assess the association of blood lead level (BLL) with cognitive performance and general intelligence, of urban school going children aged 6–16 years from ten cities of India. Secondary objective was to assess the association of anaemia with cognitive performance and general intelligence. Method: In this cross-sectional multicentric study, general intelligence was assessed by colored progressive matrices (CPM)/standard progressive matrices (SPM) test, visual-spatial ability through coding, attention and concentration ability through digit span and working memory through arithmetic tests. Blood samples of participants were collected to assess lead levels. Socioeconomic status and anthropometric measures were also collected. Results: From April 2019–February 2020, 2247 participants with equal gender distribution were enrolled from 60 schools. The median (IQR) BLL was 8.8 (4.8, 16.4) μg/dl. We found that BLL was significantly associated with attention and concentration ability and 1 μg/dl increase in BLL decreases the performance by odds of 1.02 (95 % CI 1.01–1.03). Anaemia is found to be associated with ‘borderline or dull normal’ performance for general intelligence [Adjusted Odds Ratio (AOR) = 1.93 (95 % CI 1.53–2.45)], visual-spatial [AOR = 1.35 (95 % CI 1.03–1.76)], attention and concentration [AOR = 1.30 (95 % CI 1.02–1.66)], working memory [AOR = 1.69 (95 % CI 1.34–2.12)] abilities. Conclusion: Since increasing BLL decreases cognitive performance and anaemia decreased both cognitive performance and intelligence, attempts must be made to keep BLL as low as possible and prevent exposure in school going children.