ALS usually leads to death because the muscles that control breathing and swallowing become too weak to work, causing respiratory failure and complications like infections and malnutrition.

How Does ALS Kill You?

ALS (amyotrophic lateral sclerosis) is a progressive disease that destroys the motor neurons that control voluntary muscles, including those used for walking, speaking, swallowing, and breathing. Over time, this loss of motor neurons causes widespread muscle weakness and paralysis that ultimately affects the respiratory system.

The Main Cause: Respiratory Failure

The most common way ALS leads to death is through respiratory failure. This happens in stages:

  1. Weak breathing muscles
    • The diaphragm and chest muscles weaken, making it harder to take deep breaths and fully exhale carbon dioxide.
 * At first this shows up as shortness of breath with exertion, morning headaches, or poor sleep.
  1. Carbon dioxide build‑up
    • As breathing weakens, the body cannot remove enough carbon dioxide.
 * CO₂ gradually accumulates in the blood, which can cause drowsiness, confusion, and then a decreasing level of consciousness.
  1. Quiet respiratory death
    • In late stages many people sleep most of the day, sometimes up to 20–22 hours, as CO₂ rises and the brain becomes less responsive.
 * Most individuals die very quietly in their sleep from progressive respiratory failure rather than from a sudden dramatic event.

Other Common Final Complications

Although respiratory failure is primary, several related problems often contribute.

  • Pneumonia and aspiration
    • Weak cough and swallowing muscles make it easy for saliva, food, or stomach contents to enter the lungs (aspiration).
* This can lead to recurrent pneumonia, which often accelerates respiratory failure and is a frequent listed cause of death.
  • Malnutrition and dehydration
    • Difficulty chewing and swallowing can cause weight loss and poor nutrition if feeding tubes are not used.
* Severe malnutrition weakens the body further and can indirectly hasten death.
  • Cardiovascular events
    • Large epidemiologic studies show that heart disease and cardiac arrest are also common co‑listed causes of death in people with ALS.
* These do not usually come from ALS directly but from general strain on the body and coexisting conditions.

What the Very End Often Looks Like

Experiences vary, but certain patterns are common when someone with ALS chooses not to use long‑term ventilation (no tracheostomy, no invasive life support).

  • More sleep, less awareness
    • As CO₂ slowly rises, people tend to sleep longer, become more drowsy, and are less aware of distress.
* Families often report that their loved one “just slept more and more and then didn’t wake up.”
  • Breathing changes
    • Breaths become more shallow and sometimes irregular.
    • There may be brief pauses in breathing, then quieter, slower respirations until breathing stops.
  • Usually not sudden or violent
    • Sudden catastrophic events (like a dramatic choking death) are less common than a gradual, peaceful decline with palliative care.
* Good symptom management can greatly reduce distress from air hunger, anxiety, or secretions.

Role of Palliative and Supportive Care

Specialist palliative care is recommended early in ALS to plan for the end of life and reduce suffering.

Key elements include:

  • Noninvasive ventilation (e.g., BiPAP) to support breathing and relieve air hunger for as long as desired.
  • Medications for breathlessness, anxiety, pain, and excess saliva or secretions.
  • Advance care planning so the person can state whether they want feeding tubes, ventilators, or to remain at home if possible.

With this kind of care, many people with ALS die at home, quietly, with relatively little distress reported by families.

If You’re Asking About Someone Specific

If you’re asking because you or someone you care about has ALS, it’s important to talk directly with the treating neurologist or palliative‑care team about:

  • What stage the disease is in now.
  • What to expect over the next months.
  • How symptoms like breathlessness, anxiety, and discomfort will be managed.

They can give a more personalized picture and help make sure the end‑of‑life phase is as comfortable and dignified as possible.

TL;DR: ALS kills primarily by progressively weakening the muscles needed for breathing, leading to slow respiratory failure, often with contributions from pneumonia and malnutrition; with good palliative care, the final phase is usually gradual and quiet rather than sudden or traumatic.

Information gathered from public forums or data available on the internet and portrayed here.