Alzheimer’s Disease Risk Linked To Gut Bacteria After Swedish Scientists Study Mice

Scientists around the world have been hard at work trying to discover just what causes Alzheimer’s disease, a degenerative, irreversible condition that affects more than five million Americans. Swedish researchers might have found a crucial but unlikely culprit: bacteria in the gut.

Researchers at Lund University in Sweden found that certain types of gut bacteria sped up the onset of Alzheimer’s disease, according to a study published Wednesday in the journal Scientific Reports. The team implanted gut bacteria from both healthy and diseased mice into the stomachs of mice with no bacteria present. The mice who received bacteria from diseased rodents developed significantly more plaque in the brain, of a type known as beta amyloid plaques, which build up between nerve cells in the brains of people with Alzheimer’s.

“It was striking that the mice which completely lacked bacteria developed much less plaque in the brain,” said Frida Fak Hallenius, one of the study’s researchers and part of the Food for Health Science Center at Lund University. “Our study is unique as it shows a direct causal link between gut bacteria and Alzheimer’s disease.”

That link could change the way Alzheimer's disease is approached entirely. Currently, the irreversible, progressive disease has no cure. But by addressing a direct link, researchers might be able to pinpoint ways to prevent or delay the disease, said Hallenius.

“We consider this to be a major breakthrough, as we used to only be able to give symptom relieving anti-retroviral drugs,” she said.

Though Alzheimer’s disease is the sixth leading cause of death among all adults in the U.S., much is still unknown about the progressive condition. Scientists currently attribute causes to a combination of genetic, environmental and lifestyle factors, according to the Centers for Disease Control and Prevention.

A study published earlier in February found a link between air pollution and Alzheimer’s disease, pointing to a possible environmental contributor. Researchers at the University of Southern California found that older women who lived in areas where fine particle air pollution exceeded governmental health standards were twice as likely to develop dementia, including Alzheimer’s.

The cost of care for Alzheimer’s patients, already a total of $236 billion in 2016, is expected to increase substantially over the coming years as the population in the U.S. gets older.