Nearly fifty percent of people over 85 suffer from symptoms of dementia of which Alzheimer’s disease, a progressive loss of brain cells, is the most common form. The second most common type of dementia comes from repeated strokes. This month researchers offer strong evidence that Alzheimer’s disease may be started by an infection.

The most comprehensive analysis ever of hundreds of Alzheimer’s brains found three strains of herpes virus (human herpes viruses 6A, 6B, and 7) at twice the level found in normal human brains, and the greater the number of damaged nerves, the greater the number of these three viruses in them (Neuron, June 21, 2018). The current theory is that the brains of people with Alzheimer’s disease are destroyed by a protein called beta amyloid. The damaged hippocampus, the part of the brain that governs memory, in Alzheimer’s disease patients contained high levels of the genetic material from herpes viruses. This suggests that the herpes viruses could have caused the human brain cells to make beta amyloid, the substance that destroys human brain cells.

A study from Taiwan followed more than 8,000 people diagnosed with herpes in 2000 and found that they were 2.6 times more likely as the general population to suffer dementia (Neurotherapeutics, Apr 2018;15(2):417-429). Those treated with anti-viral drugs at the time of diagnosis had their risk for dementia reduced by more than 90 percent. Another study showed that herpes viruses can cause mice brain cells to produce beta amyloid plaques (Neuron, July 12, 2018).

Human Herpes Virus-6 is Very Common
HHV-6 causes a very common skin rash called roseola in most young children (Curr Opin Virol, Dec 2014;0:91–96). That means that just about everyone has been infected at some time by HHV-6, but most people infected with this virus do not suffer from Alzheimer’s disease, probably because herpes viruses usually do not cross from the blood into the fluid surrounding your brain. However, it has been shown that herpes viruses can travel from your nose along the olfactory nerve to your brain.

These new studies do not prove that herpes viruses cause Alzheimer’s disease, but they raise important questions that need further study. Hopefully, this will be a wake-up call to the pharmaceutical industry to develop new drugs to treat viral infections. This year, extensive studies of three drugs that were supposed to help treat or prevent dementia all failed. If additional studies strengthen the link between herpes viruses and Alzheimers, perhaps new anti-viral drugs will be found to slow this frightening disease.

Checked 4/6/23