Shaking in dementia doesn’t belong to a single stage, and the answer depends heavily on which type of dementia a person has. In Alzheimer’s disease, shaking and physical rigidity are predominantly late-stage symptoms, appearing in stage 6 or 7 on clinical scales. In Lewy body dementia and Parkinson’s disease dementia, tremors can show up much earlier and may even be one of the first noticeable signs.
Shaking in Alzheimer’s Disease: Stages 6 and 7
Alzheimer’s is the most common form of dementia, so this is likely what most people searching this question have in mind. For most of the disease’s course, Alzheimer’s primarily affects memory, thinking, and behavior. Motor symptoms like shaking come late.
On the widely used Functional Assessment Staging Tool (FAST), which divides Alzheimer’s into seven stages, physical rigidity and involuntary movements typically appear in stage 7, the final stage. At this point, a person has already lost the ability to speak in full sentences (stage 7a-7b), walk without help (7c), and sit up without support (7d). Evident rigidity in major joints like the elbows is present in the great majority of patients throughout stage 7, and this stiffness can progress into permanent joint contractures. Primitive reflexes, like a grasp reflex or sucking reflex, also re-emerge in late stage 6 and into stage 7.
The shaking families notice at this point is different from the rhythmic tremor you might picture. It often looks like stiffness with occasional involuntary movements, fidgeting, or muscle jerks (myoclonus) rather than the classic back-and-forth hand tremor associated with Parkinson’s disease. Earlier in Alzheimer’s, around stage 6, patients may begin to fidget, pace, or engage in repetitive purposeless movements, but this is more behavioral than neurological in the way most people think of “shaking.”
Lewy Body Dementia: Tremors Can Appear Early
Lewy body dementia is fundamentally different from Alzheimer’s when it comes to movement. Tremors, muscle stiffness, a shuffling walk, and slowed movement can appear at any point in the disease, including very early on. Some people with Lewy body dementia develop movement problems years before significant memory loss. Others never develop noticeable tremors at all.
There are actually two related diagnoses here. If cognitive symptoms come first (or within a year of movement problems), it’s typically called dementia with Lewy bodies. If a person has Parkinson’s disease for more than a year before cognitive decline begins, it’s called Parkinson’s disease dementia. Both involve the same abnormal protein deposits in the brain, but the sequence matters for diagnosis.
Because tremors in Lewy body dementia aren’t tied to a specific stage the way they are in Alzheimer’s, spotting them early is important. A person who develops both cognitive changes and a tremor, visual hallucinations, or significant fluctuations in alertness may have Lewy body dementia rather than Alzheimer’s. This distinction matters for treatment, because certain medications used for behavioral symptoms in Alzheimer’s can be dangerous for people with Lewy body disease.
Why the Type of Dementia Matters for Treatment
Antipsychotic medications are sometimes prescribed to manage agitation, hallucinations, or aggressive behavior in dementia patients. These drugs can cause a side effect called extrapyramidal symptoms, which includes tremors, muscle stiffness, and involuntary movements that look a lot like Parkinson’s disease. In other words, some shaking in dementia patients is actually caused by their medication, not the disease itself.
This risk is especially serious for people with Lewy body dementia or Parkinson’s disease dementia. Certain antipsychotics, particularly haloperidol, should be avoided entirely in these patients because the side effects can be severe and even life-threatening. If you notice new or worsening tremors in someone with dementia who recently started a new medication, that connection is worth raising with their care team.
What’s Happening in the Brain
Tremors and shaking happen when the brain’s movement control systems break down. A cluster of structures deep in the brain called the basal ganglia normally helps coordinate smooth, intentional movement. When dementia damages these structures, the result can be tremors, rigidity, or involuntary jerking. The cerebellum, which sits at the base of the brain and fine-tunes the force and speed of every movement, can also be involved. Damage there leads to uncoordinated movements, balance problems, and a different type of tremor that worsens when reaching for objects.
In Parkinson’s-related dementias, the key problem is the loss of neurons that produce dopamine, a chemical messenger essential for smooth movement. This is why dopamine-replacing medications can help with the motor symptoms in these conditions. Alzheimer’s disease damages these movement centers too, but typically much later in the disease, which is why shaking shows up only in advanced stages.
Vascular Dementia and Other Types
Vascular dementia, caused by reduced blood flow to the brain from strokes or damaged blood vessels, doesn’t typically cause tremors in the way Lewy body or Parkinson’s dementia does. The most common physical symptoms are an unsteady walk and poor balance. However, if a stroke damages the basal ganglia or other movement-related brain regions, tremors or jerky movements can result. The timing and pattern depend entirely on where in the brain the vascular damage occurs, so there’s no predictable stage.
Shaking That Isn’t From Dementia
Not all shaking in an older person with dementia is caused by the dementia itself. Essential tremor, the most common movement disorder in adults, causes a rhythmic shaking during action, like when lifting a cup or writing. It tends to affect the hands and gets worse with age. Essential tremor looks different from a Parkinson’s-type tremor, which typically happens at rest, when the hands are still in the lap. A person can have both essential tremor and dementia without one causing the other, though research published in the journal Neurology has found that elderly-onset essential tremor is associated with a higher risk of developing dementia.
Other possible causes of new shaking include medication side effects, infections (which can cause temporary tremors, especially with fever), dehydration, low blood sugar, and anxiety. In someone already living with dementia, any sudden change in movement or behavior deserves attention, because it can signal a treatable problem layered on top of the underlying condition.