The main types of dementia, and how they differ

When someone is diagnosed with dementia, the next question is almost always 'what kind?' The answer shapes progression, effective medications, and daily care.

The most common form, 60–70% of dementia cases. Caused by beta-amyloid plaques and tau tangles. Onset is gradual, usually after 65 (early-onset exists but is uncommon).

Pattern: short-term memory goes first. Recent events, names, newly-learned information slip. Long-term memory (childhood, family stories) stays much longer. Judgment, planning, and language follow. Disease-modifying drugs (lecanemab, donanemab) modestly slow progression in early-stage Alzheimer's. Dr. Rudolph Tanzi (Harvard Medical School; Director of MassGeneral's Genetics and Aging Research Unit), speaking on the Nothing Left Unsaid podcast, May 2026, describes a promising gamma secretase modulator (GSM) he calls 'the statin of Alzheimer's.' Important context: GSM is currently Phase 1 only, with no Phase 2/3 human efficacy data yet. Lifestyle changes (his SHIELD protocol: Sleep, Handle stress, Interaction, Exercise, Learning, Diet) have the stronger evidence base today.

Reduced blood flow, often the cumulative effect of small silent strokes. 5–10% as primary diagnosis; another 10–20% mixed with Alzheimer's.

Pattern: step-wise rather than gradual. Stable for months, then a step down after a TIA or stroke. Executive function (planning, problem-solving) hit before memory. Each prevented stroke prevents another step down.

Alpha-synuclein deposits (Lewy bodies) in the brain. ~5–10% of cases. Closely related to Parkinson's dementia.

Distinctive triad: fluctuating alertness, recurring detailed visual hallucinations, Parkinson-like movement (shuffling gait, tremor, falls). REM sleep behavior disorder often precedes diagnosis by years. Critical: DLB can have fatal reactions to antipsychotics. Tell every doctor and pharmacist.

Conditions affecting the frontal and temporal lobes. ~5% of cases but striking because onset is younger (50s–60s) and personality changes precede memory.

Behavior-variant FTD (bvFTD): impulsivity, loss of social inhibition, apathy, inappropriate behavior; often misdiagnosed as midlife crisis or depression. Primary progressive aphasia variants affect language first. Memory may be relatively spared early.

Type-attribution is harder in practice than these categories suggest. Only 30–41% of people with Lewy body dementia get the correct diagnosis during life (Frontiers in Aging Neuroscience, 2023), usually misdiagnosed as Alzheimer's; that matters because antipsychotics used in AD can cause fatal reactions in LBD. 51% of behavioral-variant FTD patients received a prior psychiatric diagnosis, the correct one arriving 3.6 years later on average (UCSF Memory and Aging Center). Most older adults with dementia at death have mixed pathology (PMC9977689, 2023). Symptoms that don't fit the expected pattern warrant specialist re-evaluation.

The shape of decline matters as much as the snapshot. Vascular dementia drops in steps after silent strokes; Alzheimer's slides gradually; Lewy body fluctuates day to day; FTD changes personality before memory. A 15-minute annual visit only sees a point. Familiar's Daily Calls in Family Voices track vocabulary diversity, repetition rate, name recall, time-orientation, and mood across every call, and export the trend chart as a clinician-formatted PDF that gives the neurologist month-over-month signal: exactly the kind of shape that helps distinguish AD from vascular from LBD.

• Daily social engagement, particularly with familiar voices.
• Reminiscence Therapy: 0.78–2.34 SMD across 42 RCTs (>0.8 = large effect).
• Routine and structure: fewer surprises, more anchoring cues.
• Treat sensory loss: hearing aids, glasses.
• Cardiovascular health for vascular and mixed types; familiar music from age 15-25.