Involuntary mouth movements—such as lip smacking, chewing motions, tongue thrusting, or tremors—are common among older adults. These orofacial movements are medically termed dyskinesia, meaning abnormal, uncontrollable movement. They are often rooted in age-related physiological changes, underlying neurological conditions, or, frequently, medication side effects. Identifying the source is crucial, as the cause dictates the appropriate medical response.
Movement Disorders and the Nervous System
Involuntary movements originating in the nervous system are primary movement disorders, often involving the basal ganglia, which controls motor function. Orofacial Dyskinesia (OD) is the general term for these movements localized to the face, involving repetitive, stereotyped movements of the mouth, tongue, and jaw. OD can occur spontaneously without an identifiable cause, a phenomenon that increases with advancing age, even in individuals who have not taken psychiatric medications.
These dyskinesias often manifest as chewing, pouting, or grimacing motions, worsening with emotional stress or during voluntary movement attempts. Parkinson’s Disease is a distinct neurological cause, where the loss of dopamine-producing neurons leads to motor symptoms like tremors and rigidity. While classic Parkinsonian tremors affect the hands, they can also present as rhythmic, involuntary movements in the jaw and lips that occur at rest.
Another condition is Oromandibular Dystonia (OMD), a focal dystonia characterized by sustained or intermittent muscle contractions. These contractions cause repetitive, sometimes painful, abnormal postures or movements of the jaw, tongue, and face. OMD often involves involuntary jaw opening or closing, lip pursing, or tongue spasms, interfering with speaking and eating. When OMD occurs alongside involuntary eyelid spasms (blepharospasm), the combined condition is referred to as Meige syndrome.
Medication Side Effects and Drug-Induced Movements
A common cause of these movements in the elderly is pharmacologically induced disorders, primarily Tardive Dyskinesia (TD). “Tardive” means delayed, indicating the condition develops after a person has been taking a medication for months or years. TD is a hyperkinetic movement disorder caused by the long-term use of dopamine receptor-blocking agents, such as antipsychotics or certain anti-nausea medications like metoclopramide.
Older adults are particularly vulnerable to developing TD, even at lower dosages or after a shorter duration of treatment. The characteristic movements of TD are often peri-oral, including lip smacking, chewing motions, tongue protrusion, and grimacing. The underlying mechanism involves a hypersensitivity of dopamine receptors in the brain caused by the prolonged blocking action of the medication.
A concerning feature of TD is that the movements frequently persist, and may even worsen, after the causative medication is discontinued. This persistence classifies it as a “tardive” syndrome, distinguishing it from acute drug-induced movement issues that resolve quickly. The risk of TD is substantial, with cumulative incidences reaching over 50% after three years of first-generation antipsychotic use in older patients.
Structural and Mechanical Causes
Beyond neurological and pharmacological origins, many involuntary mouth movements stem from less severe mechanical or structural factors. The loss of teeth (edentulism) is strongly associated with an increase in spontaneous orofacial dyskinesia, sometimes called edentulous dyskinesia. This may be a subconscious effort to keep weakened mouth and facial muscles active, or it may relate to the loss of sensory feedback from the periodontal ligaments.
Poorly fitting dentures are another common mechanical trigger, causing the wearer to constantly adjust their mouth position or make chewing motions to stabilize the prosthetic. This adjustment is a physical attempt to achieve comfort or proper fit, not a movement disorder. The movements are often confined to the oral region and do not involve the tongue when the mouth is open, which helps differentiate them from neurological dyskinesias.
Xerostomia, or chronic dry mouth, is another physiological factor, highly prevalent due to polypharmacy and age-related changes in salivary glands. A person with dry mouth may frequently move their tongue, smack their lips, or make small chewing motions to stimulate saliva flow or moisten oral tissues. Age-related muscle loss (sarcopenia) also affects the jaw and tongue, potentially leading to instability or subtle motor control issues that result in small, repetitive movements.