Alzheimer’s disease is the sixth leading cause of death in the United States, but it’s probably the only one with such a grim outlook. That’s not to say cancer, diabetes, and heart disease aren’t as bad, but that they can be treated and sometimes cured, at least. There is no cure for Alzheimer’s and it’s still not entirely clear how it develops. According to a new study, it’s for these reasons, as well as others, that many doctors aren’t telling their patients when they’ve been diagnosed with the disease.

Accounting for 60 to 80 percent of dementia cases, the National Institutes of Health estimates that as many as five million Americans over 65 years old have the Alzheimer’s . It’s is a progressive, deadly disease that worsens at a faster pace than typical dementia. This pace is quickened because of the development of proteinous plaques and tangles, which hinder neuronal connections and kill them. It’s still unknown how these develop, and current treatments only improve symptoms — either way, the patient will eventually die from the disease, with the average lifespan after symptoms become apparent being eight years.

The study, from the non-profit Alzheimer’s Association, found that 45 percent of patients reported not being told they had Alzheimer’s. Oftentimes, doctors and health care providers neglect to inform patients because they see their diagnosis as a death sentence.

“I think part of it has to do with, back in the day, if someone was given the diagnosis of Alzheimer’s disease, it was the social kiss of death, because the impression was there was nothing to do,” Pierre Tariot, a geriatric psychologist and director of the Banner Alzheimer’s Institute, told The Washington Post. “And people are terribly afraid of a disease that robs you of your identity. They tend to look away.”

Another reason doctors find it hard to tell patients they had Alzheimer’s is because it’s often difficult to determine whether a person is experiencing early stages of Alzheimer’s or simply age-related memory loss. The two are profoundly different. Whereas age-related memory loss may include forgetting simple things like where the keys are or someone’s name, Alzheimer’s causes a person to forget how to conduct tasks they’ve been doing for decades, such as forgetting common words and taking longer to complete familiar tasks. It turns out the study also found people were more likely to be told they had Alzheimer’s if they were in later stages.

Researchers from the Alzheimer’s Association conducted the study by looking at Medicare records and surveys from Medicare recipients. They also surveyed family members and caregivers to ensure the patients’ Alzheimer’s wasn’t confusing them about the truth. Only 53 percent of these people said doctors told them about the patient’s diagnosis.

Speaking to NPR, Tariot said that despite the difficulty of telling patients, it should be done. While it uncomfortable at first, he said he’s learned to anticipate the questions patients will ask, such as, “Am I going to get worse” and, “When am I going to die.” He said patients are appreciative of his honesty. “People are relieved, not distressed,” he told NPR. “They’re relieved to have somebody who knows what’s going on and gives a message of at least some hope… a message that ‘We will stand by and navigate this process with you.’”