Monday, February 19, 2024

Sudden death syndrome

Sudden death syndrome (SDS) is a broad term that can describe any sudden, unexpected death from natural causes. It is not a formal condition or diagnosis and does not necessarily indicate a specific medical condition.

Sudden death syndrome (SDS) is an umbrella term for many biological scenarios leading to quick-onset and unforeseen mortality. The person involved often has little to no warning signs of illness. Even after death, an autopsy may not reveal obvious abnormalities.

This article explores what SDS is, its causes, and whether a person can prevent it. It also looks at commonly asked questions about SDS-related conditions.

How do doctors define SDS?

SDS is not a formal diagnosis: no set criteria universally define sudden death.

However, a 2023 article suggests that many experts have adopted the World Health Organization’s (WHO) definition.

It states that SDS is sudden, unexpected death from natural causes witnessed within one hour of symptom onset. If not witnessed, death occurring within 24 hours of someone seen alive and symptom-free is considered SDS.

Vs. sudden cardiac death (SCD)

People may use SDS interchangeably with sudden cardiac death (SCD), also known as sudden cardiac arrest (SCA).

SCD describes death caused by loss of heart function, occurring within one hour of any cardiovascular cause.

SDS and SCD have become synonymous. While many different diseases can result in a fatal chain reaction in the body, SCD is a common cause.

According to a 2022 comprehensive review, cardiovascular causes account for up to 73% of sudden deaths. This is compared with other conditions such as asthma, epilepsy, and intracerebral hemorrhage.

Are there symptoms or warning signs of SDS?

There is no standardized list of symptoms in SDS. Since SDS is not a single illness or disease, symptoms, if any, can vary significantly depending on the underlying cause.

For example, in the case of SCD, warning signs may be similar to any heart complication. Almost half of people report no symptoms of SCD. However, if symptoms are present, they may include:

chest discomfort
shortness of breath

Warning signs of other conditions that can lead to SDS may be subtle. For example, a person could mistake cerebral aneurysm symptoms for ordinary discomfort, such as a stiff neck or strong headache.

What causes SDS?

Numerous known and unknown processes in the body can contribute to SDS. However, cardiovascular disease plays a major role overall.

Sudden cardiac death (SCD) is the most common cause of SDS. It is a widely inclusive term that can describe a variety of cardiovascular events, such as:

sudden arrhythmia death syndromes (SADS), genetic heart conditions that alter the heart’s electrical activity, potentially causing sudden cardiac arrest
heart attack
coronary spasm
anomalous coronary origin, a coronary artery that has an abnormality
Brugada syndrome, a rare, inherited condition that can lead to irregular heartbeats
long or short QT syndrome, a condition that affects the heartbeat
myocarditis, inflammation of the heart
aortic stenosis, narrowed aortic valves

Coronary artery disease and SADS are among the most common underlying causes. Coronary artery disease may be responsible for as many as 80% of SCD deaths. According to a large-scale cohort study, SADS accounted for 53% of reviewed SCD cases.

SDS is not limited to cardiovascular events. Examples of non-cardiac conditions that can also lead to sudden death include:

pulmonary embolism, a blockage in the pulmonary arteries
brain hemorrhage
sudden infant death syndrome (SIDS)
brain aneurysm
anaphylaxis, a severe allergic reaction
hypertensive crisis, a sudden and severe increase in blood pressure
cerebral abscesses, an abscess in the brain
meningitis, inflammation of the lining that surrounds the brain and spinal cord

In many cases, the causes of SDS can never be explained. When this happens in adults, it may be referred to as sudden adult death syndrome. Similarly, unexplained infant mortality is referred to as sudden infant death syndrome.

What are the risk factors for SDS?

Due to the number of conditions that can lead to SDS, individual risk factors vary significantly.

Because SCD is the most common cause of SDS, its risk factors are among the most well-known. These include the general risk factors for adverse cardiac events, such as:

heavy alcohol consumption
tobacco use
physical inactivity
high blood pressure
living with a chronic disease, such as diabetes or kidney disease
a family history of SCD
substance misuse

Some causes of SDS can be heritable, or passed down through families. SADS, for example, are conditions passed down from parent to child. If a parent lives with a SADS condition, each child has a 50% chance of inheriting that condition.

Is prevention possible?

It may be possible to prevent SDS through chronic disease management and lifestyle changes.

For example, people at high risk of cardiovascular events can reduce their risk with lifestyle modifications and medical treatments.

Proactive disease management can also be important in preventing SDS.

For someone living with a life-threatening allergy, carrying an emergency epi-pen is one way to prevent sudden death. Similarly, for certain asthma conditions, an emergency inhaler may save a person’s life.

Not all sudden deaths can be prevented, however. Some conditions in SDS might not have modifiable risk factors, such as those influenced by genetics.

Frequently asked questions

Below are commonly asked questions about sudden death syndrome (SDS) and SCD.

How common is SDS?

Sudden deaths in the United States may account for between 150,000 and 450,000Trusted Source deaths annually.

Is SDC painful?

SDC may be accompanied by pain or discomfort immediately before heart function stops.

What is the most common underlying condition of SCD?

Coronary artery disease is one of the most common underlying conditions in SCD. It accounts for approximately 80%Trusted Source of sudden cardiac arrests.


SDS is not a formal diagnosis. It is an umbrella term that describes unexpected, sudden, natural causes of death.

SCD is the most common cause of SDS. However, other conditions can also cause SDS, such as epilepsy, cerebral hemorrhage, and asthma.

It may be possible to reduce a person’s chances of experiencing SDS with certain methods. These include making lifestyle modifications and treating underlying chronic diseases.

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