The findings, published in the Journal of Alzheimer's Disease, may challenge current thinking on the disease development and may mean dietary changes to limit iron intake could reduce the risk of developing the condition.
Led by Professor George Bartzokis of UCLA, the research team noted that until now most researchers have suggested that the onset of Alzheimer's is caused by one of two proteins, one called tau, the other beta-amyloid.
Previous work has suggested that as we age these proteins either disrupt signaling between neurons or simply kill them. However, new brain imaging studies from Bartzokis and his team suggest that iron accumulation may also play a role.
"We found that the amount of iron is increased in the hippocampus and is associated with tissue damage in patients with Alzheimer's but not in the healthy older individuals — or in the thalamus," said Bartzokis. "So the results suggest that iron accumulation may indeed contribute to the cause of Alzheimer's disease."
"The accumulation of iron in the brain may be influenced by modifying environmental factors, such as how much red meat and iron dietary supplements we consume and, in women, having hysterectomies before menopause," he said.
Bartzokis noted that while most Alzheimer's researchers focus on the buildup of tau or beta-amyloid that results in the signature plaques associated with the disease, he has long argued that the breakdown begins much further 'upstream.'
In the current study, the team tested their hypothesis that elevated tissue iron caused the tissue breakdown associated with Alzheimer's disease.
Bartzokis and his colleagues looked at two areas of the brain in patients with Alzheimer's - comparing the hippocampus, which is known to be damaged early in the disease, and the thalamus, an area that is generally not affected until the late stages.
The researchers used an MRI technique that can measure the amount of brain iron in ferritin, a protein that stores iron, in 31 patients with Alzheimer's and 68 healthy control subjects. They found that iron is increased in the hippocampus and is associated with tissue damage in that area. However increased iron was not found in the thalamus.
"It is difficult to measure iron in tissue when the tissue is already damaged," said Bartzokis. "But the MRI technology we used in this study allowed us to determine that the increase in iron is occurring together with the tissue damage."