The second most feared medical diagnosis – next to cancer – is Alzheimer’s disease, the most common cause of dementia.   What is Alzheimer’s disease?  This not such an easy question to answer as it may seem.  Ultimately, the diagnosis requires confirmation by autopsy or biopsy but even here the diagnoses is uncertain.  A diagnosis is made by clinical criteria based on typical features.

“Typical Alzheimer’s disease” mainly affects the elderly – onset over 65.   Most often Alzheimer’s disease is “sporadic” – meaning there is no prior family history.  The symptoms do not develop rapidly but rather come on slowly over the course of many years.  The first sign of possible Alzheimer’s disease is short-term memory slips such as forgetting conversations, getting lost, or forgetting events.  As the condition progresses there are deficits in skills in addition to memory such as problems with naming objects, problems with arithmetic, problems with multi-tasking, and/or problems with reasoning.  Despite withdrawal and apathy, social skills are retained in the early stages.  Progression unfolds over the course of several years.

There is a tendency to diagnose Alzheimer’s disease in everyone over 60 that displays memory loss or confusion by default.  However, there are treatable conditions that may be missed without adequate diagnostic workup.  For example there are the “worried well.”  These are persons with mild memory complaints that are difficult to differentiate from normal aging.  There is evidence that a portion of the worried well actually have very mild Alzheimer’s disease that will become clearer over the next few years.  Typical memory screenings are insensitive to these changes at a time when proactive treatment is essential.  The best place to start if you are worried is with a rigorous evaluation by a memory expert – often a neuropsychologist.

What are some common mimics of Alzheimer’s disease?  Depression is associated with and sometimes confused for Alzheimer’s disease.  However, the depression must be severe to create actual confusion, which is more tied to attention/concentration than actual short-term memory loss.  Late life depression is a risk factor for Alzheimer’s disease and, while very treatable, needs to be followed over time by memory assessments and proactive planning.

Metabolic disorders (e.g., low B12, low, diabetes, or high thyroid levels) and infections (e.g., herpes encephalitis, tertiary syphilis) may be associated with confusion and are treatable. Tumors and normal pressure hydrocephalus (shunting may make Alzheimer’s disease worse so careful differentiation is essential) are rare but need consideration.  These are very avoidable mistakes with proper medical evaluation.

Cognitive impairment due to vascular disease may closely resemble or may accompany Alzheimer’s disease.  Vascular cognitive impairment, like Alzheimer’s disease, is much more common with age.   Despite traditional dogma, vascular dementia may slowly progress rather than manifest as a “stepwise” decline.  Treatable issues like hypertension, smoking, alcohol, and diabetes need to be addressed during the evaluation.

Other mimics include frontotemporal degeneration, Lewy body disease, and posterior cortical atrophy.  Frontotemporal disorders first show up as changes in personality or expressive language deficits rather than memory loss.  Lewy body disease often has less severe memory loss, Parkinson’s features, and hallucinations.  Posterior cortical atrophy presents with problems of sequencing, spelling, and arithmetic rather than memory.

A more detailed review of these and other considerations can be found in Practical Neurology (2012, 12, 358-366).  Don’t just assume that mental changes associated with aging are by default Alzheimer’s disease and hopeless. If you have concerns, don’t put off a good memory assessment.