Alzheimer’s disease is a progressive neurodegenerative disorder that destroys connections between nerve cells, leading to the loss of memory, thinking, and cognitive functions. This deterioration causes profound changes in a person’s abilities. A common concern is whether a person with the disease can simply forget the mechanics of breathing. Breathing is not a memory that can be forgotten, but the disease does introduce respiratory complications through other mechanisms.
The Difference Between Automatic and Voluntary Breathing
The human body manages breathing through two distinct neurological systems, which allows for both continuous, life-sustaining airflow and conscious control. Automatic, involuntary breathing is orchestrated by the brainstem, specifically nuclei located in the pons and medulla oblongata. This control center maintains the continuous, rhythmic cycle of inhalation and exhalation without any conscious effort, ensuring that the body receives oxygen even during sleep or unconsciousness.
Voluntary, conscious control of breathing, however, originates in the cerebral cortex, particularly the motor cortex. This system is used when a person deliberately holds their breath, speaks, sings, or performs strenuous exercise that requires intentionally regulating airflow. The signals from the cortex override the brainstem’s automatic rhythm temporarily, but the subconscious control center remains the ultimate backup for survival. This dual-control mechanism separates the mechanical act of breathing from cognitive thought.
Brain Regions Affected by Alzheimer’s Disease
The pathology of Alzheimer’s disease is characterized by the accumulation of misfolded proteins: amyloid plaques and neurofibrillary tangles composed of tau protein. The disease typically begins its destructive course in the hippocampus, a brain structure fundamental for forming new memories. As the condition advances, the protein pathology spreads outward to the cerebral cortex, affecting areas responsible for higher cognitive functions like language, judgment, and complex thought.
While the disease primarily targets the cerebral hemispheres, the respiratory control centers in the brainstem are generally spared from widespread degeneration until the very late stages. Some specific brainstem nuclei, such as the locus coeruleus, may show early tau accumulation, but this area is involved more with sleep and emotion regulation than the core life-support functions of the medulla. The neurological structures responsible for the continuous, automatic rhythm of breathing remain intact long after cognitive functions have been severely impaired.
Why Breathing Control is Not Forgotten
The core reason a person with Alzheimer’s does not forget to breathe lies in the fundamental difference between cognitive function and autonomic regulation. “Forgetting” is a failure of memory and cognitive processing, functions that reside in the hippocampus and cerebral cortex, the areas most damaged by the disease. Breathing is a non-cognitive, involuntary reflex governed by the brainstem. The brainstem continually monitors carbon dioxide and oxygen levels in the blood and adjusts the respiratory rate accordingly, a process that requires no thought or memory. Since this lower brain structure is resistant to the primary pathology of Alzheimer’s disease, the mechanism for automatic respiration continues to function.
Actual Causes of Respiratory Decline in Advanced Alzheimer’s
Despite the preservation of the automatic breathing reflex, respiratory issues are a common and serious concern in advanced Alzheimer’s disease. These complications stem from the loss of coordination and muscle control, not from forgetting to breathe. Aspiration, where food or liquid is inhaled into the lungs instead of being swallowed, is a frequent problem. This difficulty is caused by dysphagia, or impaired swallowing, which results from neurological damage weakening the muscles and uncoordinating the complex reflexes needed to protect the airway.
Aspiration introduces bacteria into the lungs, leading to aspiration pneumonia, which is the most common cause of death in the late stages of the disease. Generalized frailty also contributes to respiratory decline through the weakening of the diaphragm and other chest muscles. The decline in physical health can introduce new respiratory challenges, such as sleep-disordered breathing. The combination of muscle weakness, poor immune function, and impaired protective reflexes makes the respiratory system vulnerable to life-threatening infections.