In a recent study published in Journal of the American Heart Association, a group of researchers evaluated the association between reductions in blood lead levels and changes in both systolic and diastolic blood pressure in American Indian adults participating in the Strong Heart Family Study (SHFS).
Study: The Contribution of Reductions in Blood Lead Levels to Reductions in Blood Pressure Levels: Longitudinal Evidence in the Strong Heart Family Study. Image credit: kurhan/Shutterstock.com
Record
United States (US) regulations, such as banning lead in various products and controlling its levels in water and air, have significantly reduced lead exposure and associated health risks. However, there are differences in exposure between different racial and ethnic groups.
Lead is a known risk factor for cardiovascular disease. Studies, including the National Health and Nutrition Examination Survey (NHANES), have shown that reduced blood lead levels in the US are associated with reduced deaths from cardiovascular disease.
The adverse effects of lead on blood pressure and heart function are well documented, particularly at high levels of exposure. However, the impact at current, lower levels of exposure is less clear.
Further research is needed to fully understand the long-term health effects of low-level lead exposure and to develop targeted strategies for prevention and treatment.
About the study
The Strong Heart Study (SHS), involving more than 4,500 American Indian adults from many tribes, was initiated to investigate cardiovascular disease and its risk factors.
The participants, aged between 45 and 74 years at the start of the study, were re-examined in several phases. The SHFS extended this research to include multigenerational cohorts.
This analysis focused on participants who provided blood samples during phases three and five of the study. Of these, 285 participants were selected for blood lead measurement.
This selection aimed to ensure gender balance and sufficient sample volume. The study compared blood lead levels using samples analyzed at two different laboratories, finding no significant differences in results.
Blood pressure was measured using standard procedures by trained personnel, and hypertension was defined based on specific criteria. Cardiac geometry and function were assessed via transthoracic echocardiograms, providing detailed information on cardiac structure and performance.
Participants’ sociodemographic, lifestyle, and health information were carefully collected, ensuring data reliability. The study also looked at various health markers, including glucose, cholesterol and kidney function.
Statistical analysis, performed using R, investigated the relationship between the reduction in blood lead level and changes in blood pressure and heart measurements. The study controlled for age, education, sex, body mass index, and smoking status.
The analysis explored potential dose-response relationships and non-linear associations, providing a comprehensive understanding of the impact of lead exposure on cardiovascular health.
Study results
The present study of 285 participants measured blood lead levels during two distinct phases. The demographic composition of these Phase 3 participants was very similar to the broader study group in terms of body mass index, gender distribution, blood pressure, and smoking status.
The mean age was 51.5 years. The study categorized participants based on the extent of reduction in their blood lead levels, revealing significant variation in baseline blood lead concentrations within these categories.
The greatest reduction in blood lead levels occurred in the tertile with the greatest reduction (>0.91 µg/dL), averaging 1.78 µg/dL. Notably, participants in this quarter were predominantly male, had a lower incidence of hypertension, and had lower fasting glucose levels at baseline.
The analysis revealed a correlation between blood lead reduction and systolic blood pressure reduction. Specifically, participants in the tertile with the most significant lead reduction had a significant reduction in systolic blood pressure, with a mean difference of -7.08 mm Hg.
This association appeared stronger after adjustment for fasting glucose and dyslipidemia. However, this trend did not manifest as a linear correlation in the flexible cubic spline model analysis.
The relationship between lead reduction and blood pressure changes only became more apparent when blood lead reduction exceeded 0.1 µg/dL.
The study also looked at changes in other heart measurements. Specifically, blood lead reduction was significantly associated with reduced ventricular septal thickness.
In addition, an increase in the early filling rate of transmission was observed, but this was limited to the highest levels of blood lead reduction, where the sample size was small.
Several sensitivity analyzes included variation in the consideration of participants’ hypertension status and adjustment for basic income needs.
Results consistently showed similar direction and strength in the relationships between blood lead changes and blood pressure outcomes as observed in the main models, suggesting a potential relationship between reduced blood lead levels and improved cardiovascular health.
