Bone loss at menopause can cause elevated levels of lead in the blood that may increase a woman's risk of high blood pressure, a study found.
Previous studies linked lead exposure in men with high blood pressure. But the new research is the first to suggest that thinning bones can release lead acquired from earlier exposure and cause health problems, said co-author Ellen Silbergeld, an environmental health researcher at Johns Hopkins University's Bloomberg School of Public Health.
Lead exposure from paint, water and other environmental sources elevates blood-lead levels and in large doses can cause poisoning, especially in children. Lead ultimately accumulates in bones and in low- level exposure may remain there for decades without serious effects. But when aging bones start to thin, lead can leak back into the blood, where it is more likely to cause damage, the researchers said.
"Loss of bone at menopause can essentially result in a latent or reexposure to lead," said Denis Nash, the lead author and a researcher with New York City's health department.
About one-fourth of the study participants had the highest blood-lead levels -- averaging 6.4 micrograms per deciliter. They were 40% more likely to have high blood pressure than those with the lowest blood-lead levels, 1 microgram per deciliter on average.
That suggests that lead in the blood has a damaging effect on blood pressure even when it's below the federal "level of concern" for childhood lead exposure, 10 micrograms per deciliter, Nash said. The federal limit for occupational exposure is 40 micrograms per deciliter.
Low levels of lead exposure and hypertension are common in U.S. adults, so "even if lead is not a main cause of hypertension, it could still be responsible for a significant number of cases of hypertension in the general population," Nash said.
The study appears in today's edition of the Journal of the American Medical Assn.
The researchers examined data on 2,165 women ages 40 to 59 who participated in a national health survey conducted from 1988 to 1994.