Concern over stigma and denial can delay the diagnosis of Alzheimer’s disease for years, which means that patients do not receive treatment that could slow the disease progress, according to a survey released on Tuesday.

When spouses or other relatives who care for patients are concerned about the stigma associated with the disease, delay of the diagnosis averages 6 years after symptoms first appear, the survey by the Alzheimer’s Foundation of America showed.

“Any delay in diagnosis is a setback for people with Alzheimer’s disease and their caregivers - and a delay of two years or more is a serious and unnecessary setback,” said Eric Hall, chief executive officer of the foundation.

Alzheimer’s disease is a progressive, degenerative disorder that attacks the brain’s nerve cells, resulting in loss of memory, impaired thinking, loss of language skills and behavioral changes. An estimated 1 in 10 persons over 65 years old and nearly half of those 85 or older have the disease.

“Living with this in silence can isolate people with Alzheimer’s disease and their caregivers, leaving them without critical support, resources, and proper treatment,” Hall said.

More than five million Americans have Alzheimer’s disease, and it is estimated that by 2050, that number could more than triple to 16 million.

According to the report, based on interviews with a nationwide cross-section of 539 U.S. adults who care for people with Alzheimer’s disease, the lack of knowledge about the disease is a barrier to diagnosis for two in five surveyed.

“Diagnosis and treatment are essential because there are treatments available…that have shown to potentially help maintain a person’s ability to think clearly and perform everyday tasks for a longer period of time than if left untreated,” said Dr. Beth Safirstein, co-president and medical director at the MD Clinical/MD Clinical Trials Foundation Inc. in Hallandale Beach, Florida.