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What is the common cause of death of patients with ALS?

Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig’s disease, is a progressive neurodegenerative disease that affects nerve cells in the brain and spinal cord. It causes loss of muscle control that eventually leads to paralysis and death. The exact cause of ALS is still unknown, but research has uncovered some of the common factors that lead to death in ALS patients.

Respiratory Failure

The most common cause of death for ALS patients is respiratory failure. As the disease progresses, it affects the muscles involved in breathing, preventing the lungs from functioning properly. Specifically, the diaphragm and intercostal muscles that support breathing weaken over time. This makes it very difficult for patients to get enough air and leads to respiratory failure.

As breathing becomes more difficult, patients often require mechanical ventilation to help support their respiration. But as the disease continues to advance, the muscles involved in coughing and swallowing also weaken. This makes it difficult to clear secretions from the lungs and increases the risk of pneumonia. Pneumonia combined with respiratory muscle failure is often the final cause of death in ALS patients.

According to research, respiratory failure accounts for around 80% of deaths in ALS patients. As breathing problems worsen, many patients choose to go on permanent ventilator support or eventually opt for hospice care emphasizing comfort instead of artificially prolonging life. But respiratory failure due to muscle paralysis remains the primary mechanism of death.

Aspiration Pneumonia

Another common cause of death for ALS patients is aspiration pneumonia. This occurs when food, saliva, or liquids are inhaled into the lungs rather than being swallowed into the esophagus. Normally, the cough reflex prevents this from happening. But in ALS patients, impaired swallowing and a weakened cough reflex increase the risk of aspiration.

When foreign substances enter the lungs, bacteria can multiply and cause an infection known as aspiration pneumonia. This is a type of pneumonia distinct from pneumonia caused by respiratory failure in ALS patients. But both aspiration pneumonia and respiratory muscle pneumonia are common complications in late-stage ALS that can lead to death.

Preventing Aspiration Pneumonia

To help prevent aspiration pneumonia, several interventions may be recommended for ALS patients:

  • Diet modifications – Avoiding difficult to swallow foods and thin liquids.
  • Upright positioning while eating.
  • Supplemental oxygen to keep oxygen levels normal.
  • Medications to reduce excess saliva production.
  • Mechanical cough assist devices.
  • Feeding tubes for nutrition if swallowing is impaired.

Malnutrition and Dehydration

As ALS advances, it becomes difficult for patients to eat and drink independently. Swallowing trouble can make it challenging to get adequate nutrition. And impaired mobility makes it harder to feed oneself or drink enough fluids.

Many ALS patients require insertion of a feeding tube at some point during their illness to prevent malnutrition. But even with tube feeding, metabolic abnormalities can occur that impact nutrition. Severe malnutrition diminishes the body’s reserves and increases susceptibility to cardiac issues or infections.

Likewise, reduced fluid intake can lead to dehydration as the disease progresses. Dehydration can cause electrolyte imbalances and exacerbate medical problems. Both malnutrition and dehydration can hasten death in ALS patients, especially in late stages when the body is already weakened by the disease.

Cardiac Issues

Research shows that ALS patients have an increased risk of cardiovascular problems compared to the general population. Abnormalities in heart rhythm, dilation of heart chambers, and heart failure occur more frequently in ALS patients.

The exact reason is unknown, but may relate to genetic factors or nutrition status. Limited mobility and advanced ALS also reduce blood flow which strains the heart. Issues like pneumonia or lung infections can further burden the heart. Weakened heart muscle or arrhythmias can ultimately lead to death in some ALS patients.

Managing Cardiac Risk

To monitor and minimize cardiac risks, ALS patients may undergo:

  • Regular EKGs to check heart rhythm.
  • Echocardiograms to evaluate heart structure and pumping ability.
  • Treatment of infections that could stress the heart.
  • Medications to regulate heart rhythm or strengthen heart function.
  • Physical therapy and range of motion exercises to improve circulation.

Loss of Immobility and Associated Complications

Gradual loss of voluntary muscle control leading to immobility is a core feature of ALS. As motor neurons degenerate, patients lose the ability to move, speak, swallow, and breathe.

Eventual paralysis and significantly impaired mobility leave patients vulnerable to complications such as:

  • Loss of muscle mass and severe muscle wasting.
  • Joint contractures causing limbs to draw inward.
  • Deep vein thrombosis and pulmonary embolism due to lack of movement.
  • Pressure injuries and sores from skin breakdown.
  • Infections such as pneumonia, urinary tract infections, and sepsis.

In late stage ALS, serious infections combined with malnutrition can culminate in death. Prolonged lack of mobility also takes a toll on the body’s physiological reserves.

Caring for the Immobile Patient

To help immobile ALS patients, caregivers should:

  • Reposition frequently to avoid sores and improve comfort.
  • Provide passive range of motion exercises to maintain joint mobility.
  • Use cushions and special mattresses to prevent pressure injuries.
  • Monitor for signs of infection and treat promptly if observed.
  • Administer blood thinners or compression stockings to prevent blood clots.

Inability to Breathe or Swallow

As previously mentioned, respiratory failure is the most common cause of death in ALS. As breathing muscles weaken, patients eventually lose the ability to breathe adequately. Declining lung function leads to hypoxia and respiratory arrest.

Likewise, worsening dysphagia or difficulty swallowing impedes the patient’s ability to consume food and water orally. This can hasten malnutrition if supplemental feeding is not provided. And aspiration of food contents into the lungs increases pneumonia risk.

Both respiratory failure and choking due to severe swallowing impairment can lead to death. At this stage, comfort focused hospice care often replaces life prolonging interventions.


While the exact cause of death varies from patient to patient, the terminal phase of ALS inevitably involves widespread paralysis and loss of essential bodily functions. Respiratory failure is the most prevalent mechanism of death, but aspiration pneumonia, cardiac abnormalities, infections, and malnutrition also contribute to mortality.

As voluntary muscle control diminishes, ALS patients require extensive care to prevent complications, maintain nutrition, and manage respiratory decline. With today’s supportive care, survival after symptom onset averages 2 to 5 years. But ultimately ALS culminates in death due to profound motor disability.

Ongoing research aims to find meaningful treatments to slow disease progression and prolong survival. But currently, palliative care focused on optimizing comfort and quality of life provides the best option for assisting ALS patients and families facing this difficult illness.