ROCHESTER, Minn. — More than 55 million people worldwide are believed to be living with dementia, according to the World Health Organization. Ronald Petersen, M.D., a neurologist and director of Mayo Clinic’s Alzheimer’s Disease Research Center, said you can’t prevent dementia, but you can reduce your risk.

Dementia is not one disease, but instead a term for a group of symptoms affecting memory, thinking and social abilities. Alzheimer’s disease is the most common form of dementia.

There are more than a dozen risk factors that people can address, Petersen said.

“They include blood pressure, smoking, obesity and diabetes,”he told the Mayo Clinic. “Sleep is an important factor. Many people have difficulty sleeping, for a variety of reasons, as they age.”

Heavy alcohol use, hearing loss and air pollution also may be risk factors.

“If you attack one or more of these, you may actually be able to reduce your risk of developing cognitive impairment as you age.”

Petersen added it is important to stay active — physically, socially and intellectually.

• Exercise

• Read books

• Go to lectures

• See family and friends

And have your hearing checked, he added.