Lead exposure in childhood ups risk of ADHD; boys more vulnerable
Early childhood exposure to lead appears to increase the risk of attention-deficit/hyperactivity disorder (ADHD), according to a recent study. Moreover, this effect is more pronounced for boys than for girls.
The study included 1,479 mother-infant pairs, in whom ADHD was diagnosed in 299 (mean gestational age 37.1±4.2 weeks; 71.24 percent male) while the remaining 1,180 were neurotypical (mean gestational age 38.5±2.5 weeks; 42.29 percent male). Electronic medical records were accessed for blood lead measurements. Multiple logistic regression analyses were used to investigate the dose-response relationship between lead exposure and ADHD risk.
When blood lead levels were considered as three distinct categories, researchers found that those with 2–4 µg/dL (odds ratio [OR], 1.08; 95 percent CI, 0.81–1.44) and 5–10 µg/dL (OR, 1.73; 10) of lead were more likely to be diagnosed with ADHD than those with <2 µg/dL of lead.
The same was true when the natural log-transformed linear trend of blood lead levels was considered (OR, 1.25; 1.01–1.56) or when lead concentrations were taken as a binary variable (<5 vs 5–10 µg/dL: OR, 1.66; 1.08–2.56).
Stratification by sex showed that at blood lead levels of 5–10 µg/dL, boys were at least seven times as likely to be diagnosed with ADHD as girls with <5 µg/dL of blood lead (OR, 7.48; 4.29–13.02; p<0.001). The risk was also higher in boys vs girls with <5 µg/dL of blood lead (OR, 3.02; 2.24–4.06; p<0.001).
In comparison, high levels of lead in the blood did not seem to increase the risk of ADHD diagnosis in girls (<5 vs 5–10 µg/dL: OR, 0.69; 0.28–1.71; p=0.426).