Whiffing menthol could snuff out symptoms of Alzheimer’s disease: study

Smells can evoke strong memories — but a certain smell may even help hold onto them and ease the symptoms of Alzheimer’s disease.

Inhaling menthol might possibly stave off the devastating memory loss and mental decline associated with the most common form of dementia, Spanish researchers have reported.

In initial animal trials, scientists from Cima Universidad de Navarra found that repeated short exposures to the minty-smelling organic compound helped regulate the test subjects’ immune systems and prevent cognitive deterioration.

“Surprisingly, we observed that short exposures to this substance for six months prevented cognitive decline in the mice with Alzheimer’s and, what is most interesting, also improved the cognitive ability of healthy young mice,” said Dr. Juan José Lasarte, the director of the Program of Immunology and Immunotherapy at Cima and principal author of the study.

The study, published in Frontiers in Immunology, said that when the researchers exposed mice to menthol aroma for one week a month over the course of six months, it lowered the animals’ levels of interleukin-1-beta, a protein that contributes to the body’s inflammatory response.

Scientists think inflammatory activity in the brain contributes to the development of Alzheimer’s by killing healthy neurons.

Dr. Noelia Casares, a researcher at the immunology and immunotherapy program, said the discovery has helped them better understand how odors help to regulate healthy brain function.

“This study is an important step toward understanding the connection between the immune system, the central nervous system and smell, as the results suggest that odors and immune modulators may play an important role in the prevention and treatment of Alzheimer’s and other diseases related to the central nervous system,” she said in the media release.

The study’s authors say the discovery of how the olfactory function impacts cognitive function may facilitate the creation of new odor-based therapies that could reverse the effects of Alzheimer’s.

They said blocking the activity of T regulatory cells, a type of immune cell which serves to suppress other immune activity, also improved the cognitive ability of mice with Alzheimer’s disease.

Menthol is a naturally occurring chemical in peppermint and other mint plants and is widely used in cosmetics as well as medicinal preparations for the relief of pain and respiratory conditions.

Menthol was first added to tobacco in the 1920s and 1930s to reduce the harshness of cigarette smoke and the irritation from nicotine. However, smoking menthol cigarettes would not be an ideal therapy for Alzheimer’s prevention, as smoking tobacco is known to cause inflammation and stress to cells, which encourages disease development.

A 2015 review of more than three dozen previous studies revealed that smokers are 30% more likely to be diagnosed with dementia and 40% more likely to get Alzheimer’s disease