With 6 million cases in the U.S. alone, Alzheimer's disease, the leading cause of dementia, is expected to become more widespread as the population continues to age. Like many memory disorders, it's also widely misunderstood. Dr. Sarah Kremen, director of the Neurobehavior Program at Cedars-Sinai, would like to change that. She answers five common questions about Alzheimer's and dementia below.  

Dr. Sarah Kremen: No. Dementia is a decline in cognition and the ability to carry out basic activities of daily life. It typically involves the loss of short-term memory, but can also include language, spatial and visual difficulties. People may find they're having trouble with things that used to be easy, like using the remote control and keeping track of bills. Different health problems that can lead to dementia—strokes, traumatic brain injuries, autoimmune disorders such as multiple sclerosis, and neurodegenerative illnesses like Alzheimer's and Parkinson's. Alzheimer's is the most common cause of dementia, which is why people often associate the two. When people ask if their loved one has Alzheimer's or dementia, they should really be asking, "Does my loved one have dementia, and if so, is it Alzheimer's?"

SK: Not always. Mild cognitive impairment can be a sign of Alzheimer's, but it doesn't have to be. Mild cognitive impairment is also linked to depression, thyroid problems, concussion and heart failure, among other conditions. Cognitive ability can go back to normal if those conditions improve.

SK: The No. 1 risk for developing Alzheimer's is age. Symptoms more commonly appear after age 65 but some people do experience them earlier. People with earlier onset symptoms may experience non-memory type symptoms first, like difficulty with visual-spatial skills. They'll struggle to put the harness on the dog. They may also have problems finding the right word and can't retain what people are saying long enough to be able to respond.

In about 1% of all cases, an autosomal dominant gene can cause the disease. (Autosomal dominant means that if a person gets even one copy of this gene from their parent, they will get Alzheimer's.) These patients get the disease in their 30s and 40s and have family members who are affected in every generation of the family. The good news is that this is very rare.

SK: We don't have medications yet to stop the disease, but there are definitely important steps everyone should take as early as possible. Your best defenses are things you already know are good for you, like a healthy diet and regular exercise.  

SK: Since Alzheimer's can start as much as 20 years before you notice any cognitive or behavioral symptoms, anything that slows down its progression may end up making a positive difference. We can't control our genetic disposition or the fact that we get older, but over the course of our lifetime 40% of our risk of dementia may be modifiable. The risk is lower for people who went to preschool, for example, or who learned a second language as children. Learning may have a neuro-protective effect, helping build cognitive reserves, which we believe may delay the onset of dementia in general and Alzheimer's specifically. Diet matters too. One study showed that people who ate cold-water fish once per week had a lower risk of Alzheimer's.

While it's hard to establish exact causal links, what's clear is that we reduce our risk of most diseases if we don't smoke, eat mindfully, exercise, maintain social contacts and keep our heart healthy and our weight down. Make these things a priority and you've taken the most important step you can to living both long and well, protecting your body and mind.  

Read: Thinking Ahead: New Screening for Cognitive Impairment