Alzheimer's Matters Blog

Alzheimer’s Versus Normal Cognitive Aging

July 17, 2014

Category: Understanding Dementia


Greek and Roman philosophers and physicians first referenced senile dementia more than 2,500 years ago. But it wasn’t until 1906, when German physician Alois Alzheimer described a “peculiar case” of presenile dementia, that the medical community began to understand that dementia is caused by disease, not normal aging.

A century later, researchers know a lot more about the biology of aging and Alzheimer’s disease. But despite this progress, more than 59 percent of adults still believe that Alzheimer’s disease is a typical part of aging. This widespread misconception means that many individuals are going undiagnosed and untreated, and that crucial research towards a cure is going unfunded.

What is Normal Cognitive Aging?

A person who is aging normally can continue with regular daily activities, like grocery shopping and paying bills. That doesn’t mean that they remain entirely unchanged. Our capacity to process information quickly and remember words and names begins to decline in our 20s. But getting older also has some benefits—our vocabulary grows, wisdom increases, and emotional resilience improves.

How is Alzheimer’s Disease Different?

When we say that a person has Alzheimer’s disease, we’re really saying that a person has dementia. This clinical syndrome is defined as experiencing mental impairment that is greater than expected for a person's age in at least two domains of cognitive function. Ninety percent of the time, one of those domains is memory—most often, short-term memory. Other domains include language, the ability to do complex motor tasks, and the ability to reason and plan abstractly.

For a person with Alzheimer’s, symptoms are progressive and severe enough to cause impairment in daily function. In other words, if a CEO can no longer do his job because he’s lost the ability reason abstractly or multitask, he is experiencing “significant” cognitive impairment.

How Do We Diagnose Alzheimer’s Disease?

Diagnosing Alzheimer’s disease means that we must first eliminate other potential causes of cognitive decline. For up to 10% of people, dementia has a potentially reversible cause, such as depression, thyroid disorders, vitamin B12 deficiency, or polypharmacy (multiple medications). Half of patients with mild cognitive impairment (MCI), a pre-dementia condition, will remain stable or improve, while the other 50% will progress to dementia in three to five years. 

Fortunately, we have brief psychological tests to determine if a person complaining of cognitive impairment is suffering from MCI or dementia. These nuanced psychological tests are calibrated according to years of education, age, and other important factors. In addition to doing a psychological test, physicians can now order a brain scan—called an amyloid PET scan—which can identify the presence of Alzheimer’s disease in a patient even before symptoms have begun. If an amyloid PET scan is negative, a doctor can say with confidence that their patient does not have Alzheimer’s disease.

Why We Need to Know the Difference?

Armed with an accurate diagnosis, patients and their caregivers can better prepare for the long road ahead—making decisions about care planning, ensuring a living will is in place, and reviewing finances.

Patients can also exercise, eat a healthy diet, and take DHA omega-3 fatty acids, which are all dementia prevention strategies with strong evidence of benefit. If they have diabetes, hypertension, or other medical risk factors for Alzheimer’s disease, they can more carefully manage these conditions. Moreover, they can volunteer for or donate to research to help us to find new drugs to prevent and treat Alzheimer’s disease—if not for themselves, than for their children, grandchildren, and the 44 million other people currently diagnosed with the disease.