A large observational study found that higher lithium levels in local drinking water were associated with more Wolff-Parkinson-White diagnoses among children. The paper, published by The Journal of Clinical Investigation on Oct. 13, compared county-level water measurements with diagnoses among California patients younger than 18.
Wolff-Parkinson-White syndrome, or WPW, involves an extra electrical pathway in the heart. The paper describes WPW and related supraventricular tachycardia as potentially highly symptomatic and, in rare cases, lethal. Because those accessory pathways develop before birth, the researchers examined whether environmental lithium exposure during pregnancy could be associated with their prevalence.
What the county-level analysis found
The California analysis included 2,329,090 patients, with an average age of 8.2 years. Of those patients, 686, or 0.03%, had been diagnosed with WPW.
Counties where drinking-water lithium levels were at or above the 75th percentile were associated with 71% greater odds of a WPW diagnosis than other areas. The reported odds ratio was 1.71, with a 95% confidence interval of 1.44 to 2.03.
The researchers also examined a second threshold. Areas where lithium exceeded a health-based screening limit had 29% greater odds of a WPW diagnosis, corresponding to an odds ratio of 1.29 and a 95% confidence interval of 1.05 to 1.58.
The paper reports similar results in a New York statewide cohort. Supporting analyses also linked higher-lithium areas with greater prevalence of supraventricular tachycardia, fainting, heart palpitations and catheter-ablation procedures.
The study shows an association, not causation
This was an ecological study: it compared area-level water data with area-level diagnosis prevalence. It did not measure how much lithium any individual child or pregnant person consumed, and it cannot establish that lithium caused WPW in a particular patient. WPW cases were identified through diagnostic codes, while county residence was used as a proxy for where children were likely to have lived during fetal development.
The authors conclude that higher drinking-water lithium was associated with more childhood-diagnosed WPW and may represent a modifiable risk factor for accessory-pathway development. That interpretation still requires research capable of measuring individual exposure and testing whether the observed relationship is causal.