Lead Exposure Linked To Increased Alzheimer’s Disease Risk

A recent American study, conducted by researchers from the University of Rhode Island, has found that monkeys exposed to trace amounts of lead during their childhood were more likely to develop Alzheimer’s disease later in life.

The study involved two groups of baby monkeys, one group were fed a milk formula containing trace amounts of lead for their first 400 days of life, while the other received a lead-free formula.

While no monkeys developed Alzheimer’s disease by the conclusion of the study which spanned 23 years, the brains of the monkeys fed the lead-laced formula had significantly higher levels of a protein called beta-amyloid which is linked to Alzheimer’s disease. and had more DNA damage than the other monkeys.

The researchers reported that while amyloid plaque development had been found in the brains of all of the adult monkeys, the plaques in the monkeys exposed to lead in infancy were more dense and numerous.

The levels of lead in the blood of the monkeys fed the lead laced formula were found to be between 19 and 26mg/dL which is similar to the levels of lead found in some children living in houses containing lead based paints and pipes.

“We’re not saying that lead exposure causes Alzheimer’s disease, but it’s a risk factor,” said Nasser Zawia of the University of Rhode Island in Kingston, who was part of the team that discovered the link.

While lead has previously been attributed to numerous health problems, especially in infants and young children where lead can stunt growth, and damage organs such as the kidneys and the brain this is the first study that suggests a direct link between lead and Alzheimer’s disease.

Lead is most commonly found in lead based paints, pipes some enamel and ceramic pots and cookware, and through automotive and industrial emissions although the majority of countries have banned lead additives from petrol.

The study appears in the January 2nd, 2008 edition of The Journal of Neuroscience.

Although no human studies have shown a direct link between lead exposure and Alzheimer’s disease, a 2003 study published in the journal Epidemiology found that high levels of lead in the blood and patella bone of elderly men were associated with lower scores in the Mini Mental Status Exam (MMSE), a widely used test of cognitive function. Those in the highest quartile for blood lead levels compared to the lowest quartile had 3.4 times higher odds of scoring less than 24/30 on the MMSE test. MMSE scores also declined faster with age in individuals with high lead levels leading the authors to conclude that “lead exposure might be a significant risk factor for age-associated cognitive decline and deserves further study”.