A tremor is an involuntary, rhythmic muscle contraction that results in a shaking movement in one or more parts of the body. While tremors can affect the head, voice, torso, or legs, they are most commonly observed in the hands. Tremors are a symptom, not a disease, and are particularly common among the elderly population. A medical evaluation can determine if the underlying cause is a chronic neurological condition or a temporary, treatable trigger. This overview explores the conditions that cause them in older adults.
Understanding Tremor Types
The first step in diagnosing a tremor involves classifying it based on when the movement occurs, which provides immediate clues about its origin. The two main classifications are resting tremors and action tremors, which are further divided into subtypes.
A resting tremor is visible when the muscle is completely relaxed and fully supported against gravity, such as when the hands are resting in the lap. This type of tremor typically disappears or lessens significantly when the person initiates a voluntary movement. In contrast, an action tremor occurs during any voluntary muscle contraction.
Action tremors are subdivided into postural and kinetic types. A postural tremor is present when a limb is actively held in a fixed position against gravity, such as holding the arms outstretched. A kinetic tremor occurs during any voluntary movement, and this category includes intention tremors, which worsen as the limb approaches a target, like touching a finger to the nose.
Primary Neurological Disorders
The two most frequently encountered chronic neurological causes of tremor in the elderly are Essential Tremor and the tremor associated with Parkinson’s Disease (PD). These conditions are differentiated primarily by the type of tremor they produce and the presence of other associated symptoms. Correct identification is crucial for effective management.
Essential Tremor (ET) is the most common movement disorder, affecting approximately 4% of the population over age 65. This condition is characterized predominantly by an action tremor, meaning it is most noticeable during postural holding or kinetic movement, such as writing or drinking from a cup. The shaking is typically bilateral, affecting the hands and forearms, but it can also involve the head, voice, or jaw.
The tremor frequency in ET is usually between 4 and 8 Hz, and it tends to be largely symmetric, though slight asymmetry is possible. While ET is slowly progressive, its defining feature is the absence of other neurological signs like rigidity or extreme slowness of movement. Family history is common.
The tremor linked to Parkinson’s Disease (PD) presents primarily as a resting tremor. This tremor is often described as a “pill-rolling” motion, involving the rhythmic movement of the thumb and forefinger as if rolling a small object. It usually begins asymmetrically, affecting one side of the body more than the other, and is most pronounced when the limb is fully relaxed.
The typical PD tremor has a lower frequency, ranging from 4 to 6 Hz, compared to Essential Tremor. The diagnosis of PD requires the presence of the tremor along with other characteristic motor symptoms, such as bradykinesia (slowness of movement) and rigidity (stiffness). This combination of features is what distinguishes Parkinsonian tremor.
Secondary and Reversible Triggers
Not all tremors are caused by chronic neurological disorders; many result from temporary or treatable factors, often categorized as enhanced physiological tremors. Identifying these secondary causes is important because addressing the underlying trigger can often resolve or significantly reduce the shaking. A common cause is a side effect from medication, known as drug-induced tremor.
Several classes of drugs are known to cause or worsen tremors, including some antidepressants like SSRIs, mood stabilizers such as lithium and valproate, and certain asthma medications. These substances can affect the nervous system’s balance, leading to involuntary muscle contractions. Reviewing all current prescriptions is an important step in the diagnostic process.
Metabolic issues frequently manifest as tremors, notably hyperthyroidism and low blood sugar. Hyperthyroidism, an overactive thyroid gland, accelerates the body’s metabolism and increases nervous system stimuli, resulting in a fine, rapid hand tremor. Hypoglycemia, or low blood sugar, often causes shakiness due to the body’s stress response.
Lifestyle factors can temporarily induce or exaggerate a tremor. Excessive consumption of caffeine is a common stimulant that can cause jitters and intensify an existing tremor. Stress, anxiety, or fatigue can temporarily increase tremor amplitude. Alcohol withdrawal is another important cause, as the sudden cessation of heavy drinking overexcites the central nervous system, resulting in prominent tremors known as “the shakes.”