Study: Snoring, Alzheimer's Link?

June 12, 2001 -- Could snoring increase your chances of getting Alzheimer's disease?

Some intriguing, but very preliminary, research seems to suggest that night wood sawing could be one factor in the pathway to the very complex neurodegenerative Alzheimer's disease that currently affects 4 million Americans.

Stanford University scientists have found that individuals with a particular genetic marker, called APOE4, were twice as likely than non-carriers to suffer from sleep apnea, a dangerous nighttime breathing disorder characterized by snoring.

The APOE4 marker also predisposes carriers to the development of Alzheimer's and cardiovascular disease.

APOE4 is one variant of the apolipoprotein E gene, which was first identified as playing a role in cholesterol metabolism.

Complex Interactions at Play

The researchers suggest that complex interactions between breathing patterns during sleep, cholesterol metabolism and mental status may be playing a role in all these diseases. But more research needs to be done to understand the relationships.

"Sleep apnea may actually be the symptom of a very early form of brain injury," says Dr. Emmanuel Mignot, director of the center for narcolepsy at Stanford's Center for Human Sleep Research. The research is published in the latest issue of the Journal of the American Medical Association.

Apnea sufferers experience short bouts of breathing cessation many times during the night, leading to a decreased amount of oxygen in their blood. They are apt to snore.

Untreated, sleep apnea can cause high blood pressure and other cardiovascular disease, memory problems, weight gain, impotency, and headaches, doctors say. People with sleep apnea are more likely to die of heart attacks than non-sufferers.

A machine that pushes air at a high pressure through the nasal passageways is the most common treatment for sleep apnea.

The disease can cluster in families, and studies have shown that Alzheimer's patients are more likely to suffer from sleep apnea than the general population.

APOE4 Linked to Apnea, Alzheimer's

In the research, Mignot and colleagues studied the apolipoprotein E gene in blood samples of 719 middle-aged adults who were participating in a sleep apnea study.

The researchers found that 28 percent of the subjects carried at least one copy of the APOE4 gene. (Each of us has two copies of the apolipoprotein gene, one from your mother and the other from your father.)

Nearly 12 percent of the APOE4 carriers suffered from moderate to severe sleep apnea compared to 7 percent of non-carriers, a statistically significant difference.

Experts called these findings intriguing, but say they need to be replicated and further studied.

More Research Needed

"People with sleep apnea should not extrapolate from this study that they are at risk for Alzheimer's disease," says Barbara Pettersen, a genetic counselor from Bend, Ore. "The study just shows a correlation at this point that needs further study."

People with sleep apnea should get treated regardless of these findings, she says. There are probably other factors besides the APOE4 marker that contribute to sleep apnea and Alzheimer's disease.

"But the findings are interesting," Pettersen says. "The possibility that these three disorders may have a common association in some proportion of cases is a significant scientific breakthrough. It allows researchers to further investigate the molecular and biochemical basis for the association," which could lead to future prevention and treatment strategies.