Children’s exposure to cocaine detected by hair analysis: a systematic review and meta-analysis

Background: Cocaine is a widespread drug of abuse to which children can also be exposed. The modes of exposure may vary depending on the age of the child. In addition to blood and urine analysis, hair analysis is currently used in some clinical contexts to investigate children’s exposure to drugs of abuse, including cocaine. This systematic review aims to collect data on children’s exposure to cocaine proven by hair analysis, and to understand whether the concentration of cocaine in the hair of children varies with age, potentially providing insights into the nature of their exposure. Methods: This review was conducted in PubMed (including PubMed Central and Medline), Web of Science (Core Collection), and grey literature databases including Web of Science Preprint Citation Index, OpenGrey.eu, and Grey Literature Report, from inception until July 15, 2024. Cross-sectional studies, case series, and case reports where cocaine was detected in children’s hair using mass spectrometry techniques, and concentrations reported, were included. Study selection and data extraction were conducted independently by two reviewers. Results: The systematic review included 21 studies. Ten studies were eligible for meta-analysis. Cocaine median concentrations (ng/mg) at hair analysis were 1.17 [95% CI (0.19, 7.17)] in children under one year and 0.39 [95% CI (0.13, 1.13)] in children over one year. The heterogeneity tests indicated high between-study heterogeneity (I2 = 93.76% in studies including children under one year; I2 = 93.92% in studies including older children). Conclusions: The finding of higher median concentration of cocaine in hair of infants under one year should be cautiously read, considering the characteristics of hair of young children and the influence of possible exposure occurring even or only in utero. The heterogeneity between the studies suggests differences in the study populations, and these may be reflected in terms of exposure levels. Given this heterogeneity and the potential for publication bias, further research involving larger populations and employing more rigorous methodologies is essential. The assessment of these cases cannot therefore be based on hair analysis alone, but must consider the analysis of other biological matrices, the history of the child and family, and information on the living environment.