有关铅中毒

铅会使脑内去钾肾上腺素、多巴胺和5-羟色胺的含量明显降低，造成神经质传导阻滞，引起记忆力衰退、痴呆症、智力发育障碍等症。因此是脑细胞的一大“杀手”。

人体摄铅过多，还会直接破坏神经细胞内遗传物质脱氧核糖核酸的功能，不仅易使人患痴呆症，而且还会使人脸色灰暗过早衰老。

含铅食物主要是爆米花、松花蛋等。需要注意的是，“无铅松花蛋”的铅含量并不等于零，只是低于相应的国家标准，同样不宜大量食用。

Lead Exposure Takes Heavy Toll on Cognitive Function
(这篇文章说铅中毒积累老年后将引起智力衰退)

Caroline Cassels
Information from Industry
Antibiotic Treatment for Many Outpatient and Inpatient Bacterial Infections
Learn more about high-dose, short-course therapy, including PK/PD parameters, clinical benefits, and doctor and patient benefits.

September 21, 2006 — Long-term community lead exposure contributes to impairment of cognitive function among older adults that is equivalent to 2 to 6 more years of age, a new study has found.

In the large cross-sectional study of older adults aged 50 to 70 years, investigators found that environmental exposure to higher levels of lead when lead was extensively used in commercial products, before the 1980s, resulted in poor cognitive outcomes. This finding suggests that a proportion of what is considered "normal" aging of the brain may in fact be due to the effects of lead exposure.

"Our findings show cumulative exposure over the lifetime, at pre-1980s levels, has a persistent effect on cognitive ability across all cognitive domains that can be observed later in life," the study's first author Regina Shih, PhD, from the Johns Hopkins Bloomberg School of Public Health in Baltimore, Maryland, told Medscape.

The study appears online September 13 in Neurology.

Higher Levels in African Americans

The study included 985 ethnically and socioeconomically diverse, urban-dwelling adults from the Baltimore area who were randomly selected to participate in the study.

Recent lead exposure was assessed by blood levels, while long-term exposure was determined through measurement of lead levels in the tibia. Mean blood levels of lead were low (3.5 μg/dL), while mean tibia levels were moderate to high (18.7 μg/g).

Furthermore, on average, tibia lead levels were 30% higher in African Americans than in whites. Previous population-based studies have shown that African Americans and other minorities tend to have higher blood lead levels than their white counterparts. Since lead accumulates in bone over a lifetime, this is the likely explanation for this finding, said Dr. Shih.

Pervasive Effect

Participants' cognitive function was assessed using a series of tests that measured language, processing speed, eye-hand coordination, executive functioning, verbal memory and learning, and visual memory.

After controlling for age, ***, and the presence of the APOE-e4 allele, the investigators found cognitive decrements were strongly associated with cumulative exposure as indicated by higher tibia levels and that this was true for all 7 domains tested.

"We were very surprised to find such a pervasive effect of lead and did not expect the magnitude of the association between lead exposure and all cognitive domains to be so large--in 1 case as much as 60% of the age association," said Dr. Shih.

First Representative Study

Previous studies of lead exposure and cognitive function in adults have been conducted in occupational lead workers. However, this study, which included both ***es, as well as white and African American participants from a range of socioeconomic backgrounds, is the first to look at the impact of lead exposure in a representative population-based sample.

At this point, said Dr. Shih, there is no known medical treatment to prevent the deleterious effects of lead exposure on the brain.

Depending on lead level, chelation therapy to remove lead due to low-level environmental exposure is generally not recommended and may in fact do more harm than good, as it could cause a redistribution of lead from the bone to the bloodstream that would subsequently reach the brain.

However, she said, clinicians can help patients reduce their risk of cognitive decline by encouraging them to consume a diet high in antioxidants and remain "cognitively active."

Good News, Bad News


Extensive efforts to ban many lead-containing consumer products have resulted in a "drastic" decline in blood lead levels since the 1980s. However, said Dr. Shih, many adults currently older than 30 years have been exposed to those higher pre-1980s levels of lead for a large portion of their lives.

"At this point, there is no evidence of lead-related dementia in adults solely exposed to environmental lead. But our findings suggest that lead may contribute to what has been termed 'normal cognitive aging.' Considering our increasing aging population, this is problematic. Whether long-term lead exposure is related to abnormal cognitive aging or is a risk factor for dementias such as Alzheimer's is a question for future research," she said.

Neurology. Published online September 13, 2006.