Alzheimer’s disease is the most common type of dementia—a general term that refers to difficulties with memory or reasoning that are serious enough to interfere with daily life. About one in nine people in the United States aged 65 and older has Alzheimer’s disease, according to the Alzheimer’s Association.

In this Q&A, Tianxu Xia, MD, a behavioral neurologist and neuropsychiatrist at The Mount Sinai Hospital, explains what causes Alzheimer’s disease, what are some of the early symptoms to watch for, and what you can do to support a healthy brain. Dr. Xia is also an Assistant Professor of Neurology and Psychiatry at the Icahn School of Medicine at Mount Sinai and a practitioner of the interdisciplinary team at The Barbara and Maurice Deane Healthy Brain Initiative.

Tianxu Xia, MD.

What causes Alzheimer’s disease?

Alzheimer’s disease is usually a slow progressive illness that begins probably many years before any symptoms even emerge. The hallmark pathologies of Alzheimer disease are the accumulation of two abnormal proteins in the human brain. One is called beta-amyloid, and the other one is called tau protein. These two proteins are neurotoxic in nature, and eventually lead to the death of the brain cells and subsequent brain shrinkage.

What are the early signs and symptoms of Alzheimer’s disease?

Neurological symptoms are closely correlated to anatomical locations. Alzheimer’s disease typically first shrinks the structure called the “hippocampal formation,” which is the short-term memory center of the human brain. If that happens, short term memory lapse is the most common early sign of the disease. People should pay attention if they find they are beginning to forget recent events, conversations, or medical appointments. Or if they are repeating themselves and constantly misplacing and losing items. Another part of the brain often affected by the Alzheimer’s pathology is called the parietal lobe, which is located at the back of our brain. It is the key component for the processing of visual-spatial information, language, and higher cognitive functions such as calculation, attention, and executive functioning. Therefore, aside from memory difficulty, a patient with Alzheimer’s disease may or may not experience early challenges in navigating, word-finding, planning, and figuring out complex day-to-day tasks, like how to manage their own finances and medical care.

What is the difference between Alzheimer’s disease and dementia?

Those two terms have been used interchangeably historically and that has caused confusion among patients, even among medical professionals. I like to explain to my patients that when it comes to the cognitive decline in the elderly, there are three tiers.

• Normal: Normal aging of brain means the brain is getting smaller. We are becoming a little bit more forgetful. Everything is taking longer for us to memorize, to learn new things, as well as even simple things like searching for a word.
• Mild cognitive impairment (MCI): MCI is a very important concept. However, many people are not familiar with it. In this tier, there is cognitive decline beyond what is normal and which can be detected by cognitive testing tools. However, a person’s ability to carry out everyday functions remains intact.
•  Dementia: Dementia is not a disease but a clinical condition. When people enter a stage of dementia, that means they can have impairment that is severe enough to affect their ability to perform daily activities independently.

Many conditions can cause MCI and dementia. Alzheimer’s disease is just one of them. But it is the most common one.

Georges Naasan, MD, right, Co-Medical Director of the Barbara and Maurice Deane Healthy Brain Initiative, evaluates a patient.

If I was diagnosed with MCI, what does that mean?

Among those with MCI, about 15 percent develop dementia after two years. Some, though, return to normal cognition or do not have additional cognitive decline. Since MCI is an important intermediate stage between normal aging and dementia, identifying which individuals with MCI are more likely to develop dementia is a major goal for researchers.

What can we do to help maintain a healthy brain?

Brain heath is highly dependent on the health of your heart and blood vessels. A heathy heart ensures that enough blood is pumped to the brain. Healthy blood vessels enable oxygen and nutrient-rich blood to reach the brain so it can function normally. Maintaining your overall physical health and minimizing the neurovascular risk factors are essential. Optimizing your blood pressure and levels of sugar and cholesterol are a solid foundation to face brain aging. Studies also show continuous social and cognitively stimulating activities may help build cognitive reserve to compensate the decline caused by brain aging.

What is some of the current research into Alzheimer’s disease?

In the last 20 years, scientists and physicians have vastly expanded our understanding of Alzheimer’s disease and other neurodegenerative illnesses. Their efforts in research have produced more accessible and accurate testing methods to help us detect the disease in the early stages, as well as promising therapies now being studied in clinical trials. We need more patients to participate in Alzheimer disease research, so that we are able to accelerate the progress of defeating this devastating illness.