Researchers Discover Alzheimer's "Subtypes"

By Sondra Forsyth

Alzheimer’s disease, long thought to be a single disease, really consists of three distinct subtypes, according to a UCLA study.

The discovery could eventually lead to new treatments for the debilitating neurological disorder.

Additionally, the study found that one of the three variations, the cortical subtype, appears to be fundamentally a different condition than the other two, said Dr. Dale Bredesen, the study’s author, a UCLA professor of neurology and member of the Easton Laboratory for Neurodegenerative Disease Research.

“Because the presentation varies from person to person, there has been suspicion for years that Alzheimer’s represents more than one illness,” said Bredesen, who also is the founding president of the Buck Institute for Research on Aging. “When laboratory tests go beyond the usual tests, we find these three distinct subtypes.

“The important implications of this are that the optimal treatment may be different for each group, there may be different causes, and, for future clinical trials, it may be helpful to study specific groups separately.”

The subtypes are:

Inflammatory, in which markers such as C-reactive protein and serum albumin to globulin ratios are increased.

Non-inflammatory, in which these markers are not increased but other metabolic abnormalities are present.

Cortical, which affects relatively young individuals and appears more widely distributed across the brain than the other subtypes of Alzheimer’s. It typically does not seem to cause memory loss at first, but people with this subtype of the disease tend to lose language skills. It is often misdiagnosed, typically affects people who do not have an Alzheimer’s-related gene and is associated with a significant zinc deficiency.

The findings of the two-year study, which involved metabolic testing of 50 people, appear in the current issue of the peer-reviewed journal Aging.

No effective therapy for Alzheimer’s exists. And scientists have yet to completely identify the cause, although multiple studies have pointed to metabolic abnormalities such as insulin resistance, hormonal deficiencies and hyperhomocysteinemia, a condition characterized by an abnormally high level of an amino acid in the blood.

In a 2014 paper, Bredesen showed that making lifestyle, exercise and diet changes designed to improve the body’s metabolism reversed cognitive decline in nine out of 10 patients with early Alzheimer’s disease or its precursors.