Investigators tested lead levels in the blood, tibias, and patellae of 475 adult men, 97 with resistant hypertension.
After adjusting for demographics, lifestyle, and socioeconomic factors, the team found that the risk for resistant hypertension was 19% higher with every 15 μg/g increase in tibia lead levels — an association not found in the blood or patella
“We found that lead measured in the tibia, the shin bone, is associated with a higher risk of resistant hypertension, and this association was independent of important risk factors for hypertension,” lead author Sung Kyun Park, ScD, MPH, associate professor of epidemiology and environmental health sciences, University of Michigan School of Public Health, Ann Arbor, told theheart.org | Medscape Cardiology.
“Our study suggests that physicians may also want to ask patients about past lead exposure,” he said.
The study was published online October 24 in the Journal of the American Heart Association.
Interference With Vasculature
“Lead has been studied for its potential role in elevated and volatile blood pressure,” the authors write.
Prolonged exposure to lead has been found to predict the development of hypertension, and cohort studies have linked blood lead levels to increased blood pressure (BP) and hypertensive risk.
“Lead has been shown to interfere with the function of vasculature and endothelial cells through increases in the RAS [rennin–angiotensin system] and vasoconstricting prostanoids, in combination with decreases in the potent vasodilator nitric oxide,” Park explained.
“Low levels of lead can lead to marked decrease in nitric oxide availability, and lead can upregulate the RAS activity via increased angiotensin-converting enzyme and angiotensin II receptor type 1, which results in arterial contraction,” he continued.
He recounted that the motivation of the study was to understand “why some patients need more drugs to control high blood pressure than others, [which is] poorly understood.”