Repetitive chewing, lip-smacking, or tongue movements when an older person is not eating is a common phenomenon. This involuntary behavior is often referred to as “phantom chewing” or “mouthing,” representing an uncontrolled movement of the facial and oral muscles. While the behavior can be a response to simple physical discomfort, it frequently indicates an underlying neurological change or a side effect of certain long-term medications. Understanding the source of these movements is the first step toward management and treatment.
Understanding Involuntary Orofacial Movements
Many involuntary movements of the mouth and face are classified as Dyskinesia, which describes abnormal, uncontrolled motion. These chewing motions specifically fall under Orofacial Dyskinesia, relating to the mouth, tongue, and jaw muscles. The origin of these movements is typically traced back to the basal ganglia, a group of structures deep within the brain responsible for regulating motor control. The basal ganglia act like a filter, ensuring that only desired movements are executed while unwanted movements are suppressed.
When the basal ganglia circuits become damaged or dysfunctional, this filtering process fails, leading to uncontrolled, repetitive movements. In some cases, these movements are classified as “spontaneous” or “idiopathic” orofacial dyskinesia, meaning no clear cause is identified other than age-related neurodegenerative change. This spontaneous form may affect a notable percentage of older individuals, even those who have never taken medications associated with movement disorders.
In addition to idiopathic forms, conditions that affect the basal ganglia can also lead to these symptoms. Parkinson’s disease, for example, involves the loss of dopamine-producing cells in this brain region. While the disease is generally associated with tremors and slowed movement, the complex neurochemical changes can sometimes result in involuntary mouth and jaw movements. Furthermore, the long-term use of Levodopa, a common medication used to manage Parkinson’s symptoms, can also induce its own form of dyskinesia.
Medication-Related Dyskinesias
A common cause of involuntary chewing motions in older adults is Tardive Dyskinesia (TD), a movement disorder that develops after prolonged use of certain medications. The term “tardive” means delayed, reflecting that symptoms often appear months or even years after starting the drug.
Tardive Dyskinesia is primarily linked to drugs that block dopamine receptors in the brain, often used to treat psychiatric or gastrointestinal conditions. These medications include first-generation antipsychotics, such as Haloperidol or Chlorpromazine, prescribed for decades to manage conditions like schizophrenia. The chronic blocking of dopamine receptors is thought to lead to hypersensitivity in the dopamine system, resulting in uncontrolled muscle movements.
A relevant cause for many older individuals is the use of certain anti-nausea or digestive motility medications. Specific drugs, such as metoclopramide (used to treat chronic acid reflux or delayed stomach emptying), carry a risk of causing Tardive Dyskinesia, especially with long-term use. TD symptoms are frequently concentrated in the face and mouth, presenting as lip-smacking, tongue protrusion, or rhythmic chewing motions. These movements can become permanent even after the causative medication is stopped.
Non-Neurological and Environmental Factors
Not all involuntary mouth movements stem from neurological or medication-induced changes; some are triggered by physical discomforts in the oral cavity. Xerostomia, commonly known as chronic dry mouth, is a frequent contributor. Many older adults take medications for high blood pressure or depression that reduce saliva production, leading to persistent dryness.
An individual with dry mouth may engage in repetitive chewing or tongue movements in an attempt to stimulate the salivary glands and moisten the mouth. This is often accompanied by an increased need to drink water or difficulty speaking or swallowing. Another physical cause involves poorly fitting or loose dental appliances, such as dentures. A person may constantly adjust the denture or move their jaw to find a comfortable position, creating the appearance of habitual chewing.
The constant motion may also develop as a learned behavior or a response to stress. Repetitive jaw movements can be a physical manifestation of anxiety or stress, similar to fidgeting with hands. In the context of cognitive decline, a person with dementia might exhibit perseveration—a tendency to repeat a gesture or action—which can manifest as persistent mouthing or chewing.
Next Steps and Seeking Medical Guidance
If you observe a pattern of involuntary chewing or mouthing, the first step is to thoroughly review the individual’s current and past medication list. Look for drugs known to affect dopamine or those known to cause dry mouth, including both prescription and over-the-counter medications. Never abruptly stop a prescribed medication, but bring the full list to a healthcare professional for evaluation.
It is helpful to document the movements, noting their frequency, the time of day they occur, and any factors that seem to worsen or briefly stop them. This detailed information will assist a doctor in determining whether the cause is a reversible factor (like a dental issue or dry mouth) or a chronic neurological condition. Managing these movements often involves adjusting medication dosages, switching to alternative drugs, or treating underlying causes like dry mouth with specific therapies.