Women who accumulate the highest lead levels are more likely to experience early menopause, according to new research epublished January 3, 2014.
In a study of 401 women from the Boston area, those with the highest levels of lead in their shinbone were 5 times more likely than women with the lowest levels to experience menopause before the age of 45, according to the report from the Harvard School of Public Health.
It is the first study to link long-term, low-level lead exposure to early menopause, a condition that raises the risk of heart disease and other health effects.
“The success in reducing external lead exposures in the US may mean that women entering menopause today are at less risk of lead-associated earlier age at menopause than we observed,” the authors wrote in the study published online at Environmental Health Perspectives last week.
Nevertheless, they added that “the possibility remains that further reductions in lead levels could still improve the health of women as they age.”
The researchers compared the age of menopause with lead levels in the blood, shinbone (tibia) and kneecap (patella) of women enrolled in the Nurses’ Health Study, a group tracked by health researchers since 1976. Breaking the women into three groups based on the levels of lead in their tibias, researchers found that the average age of menopause for women with the highest levels was 1.21 years younger than those with the lowest levels.
There was no association between blood or patella bone lead levels and age of menopause onset.
It is not clear why only tibia levels were associated with earlier menopause. It could be that lead doesn’t stay in blood too long and bone lead levels are indicative of long-term exposure, the study authors said.
The study is limited in that the bone lead measures were made mostly after menopause for most women. In addition, only 23 of the women experienced menopause before the age of 45, which is a small sample. The average age was 51.
Results: Higher tibia lead level was associated with younger age at menopause. In adjusted analyses, the average age of menopause for women in the highest tertile of tibia lead was 1.21 years younger (95% CI: –2.08, –0.35) than for women in the lowest tertile (p-trend = 0.006). Although the number of cases was small (n = 23), the odds ratio for early menopause (< 45 years of age) was 5.30 (95% CI: 1.42, 19.78) for women in the highest tertile of tibia lead compared with those in the lowest tertile (p-trend = 0.006).