Sudden Infant Death Syndrome (SIDS)

Definition and Epidemiology

Definition

Sudden infant death syndrome (SIDS) is the sudden, unexplained death of a child in infancy (< 1 year of age) with no identifiable cause after examination, clinical case review, and autopsy.

Epidemiology

• Leading cause of death in children between 1 and 12 months of age in the United States
  • Peak incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency: 2–4 months
  • > 90% occur before 6 months of age
• Incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency: 1,529 deaths attributed to SIDS in the United States in 2022
• Nearly 3 times as common in Black and Native American/Alaskan Native families
• The incidence Incidence The number of new cases of a given disease during a given period in a specified population. It also is used for the rate at which new events occur in a defined population. It is differentiated from prevalence, which refers to all cases in the population at a given time. Measures of Disease Frequency of SIDS has significantly decreased in developing countries due to “back to sleep Sleep A readily reversible suspension of sensorimotor interaction with the environment, usually associated with recumbency and immobility. Physiology of Sleep” public health campaigns.

Etiology and Pathophysiology

Etiology

The most likely cause of SIDS involves a multifactorial genesis in particularly vulnerable babies, in which internal and external factors work together.

• Vulnerable infants: unable to detect or respond to hypoxia Hypoxia Sub-optimal oxygen levels in the ambient air of living organisms. Ischemic Cell Damage/ hypercapnia Hypercapnia A clinical manifestation of abnormal increase in the amount of carbon dioxide in arterial blood. Neonatal Respiratory Distress Syndrome
  • Premature Premature Childbirth before 37 weeks of pregnancy (259 days from the first day of the mother’s last menstrual period, or 245 days after fertilization). Necrotizing Enterocolitis infants
  • Infants with brainstem abnormalities
  • Premature Premature Childbirth before 37 weeks of pregnancy (259 days from the first day of the mother’s last menstrual period, or 245 days after fertilization). Necrotizing Enterocolitis/low-birth-weight infants
  • Previous brief resolved unexplained event Brief Resolved Unexplained Event A brief resolved unexplained event (BRUE) is defined as a reported, sudden, brief (< 1 minute) event in a child < 1 year of age, which is resolved at the time of presentation. The definition includes ≥ 1 finding of either change in color (cyanosis or pallor), breathing pattern (absent, decreased, or irregular), muscle tone (hypertonia or hypotonia), or level of consciousness. Brief Resolved Unexplained Event ( BRUE BRUE A brief resolved unexplained event (BRUE) is defined as a reported, sudden, brief (< 1 minute) event in a child < 1 year of age, which is resolved at the time of presentation. The definition includes ≥ 1 finding of either change in color (cyanosis or pallor), breathing pattern (absent, decreased, or irregular), muscle tone (hypertonia or hypotonia), or level of consciousness. Brief Resolved Unexplained Event)
• Maternal risk factors
  • Maternal age younger than 20
  • Delayed prenatal care Prenatal care Prenatal care is a systematic and periodic assessment of pregnant women during gestation to assure the best health outcome for the mother and her fetus. Prenatal care prevents and identifies maternal and fetal problems that adversely affect the pregnancy outcome. Prenatal Care
  • Low socioeconomic status
  • Parental smoking Smoking Willful or deliberate act of inhaling and exhaling smoke from burning substances or agents held by hand. Interstitial Lung Diseases
• Environmental risk factors (many of these are modifiable risks)
  • Unsafe sleeping practices 
    • Allowing infant to sleep Sleep A readily reversible suspension of sensorimotor interaction with the environment, usually associated with recumbency and immobility. Physiology of Sleep in prone position
    • Bed-sharing (co-sleeping)
    • Cluttered cribs (toys, pillows, blankets, etc ETC The electron transport chain (ETC) sends electrons through a series of proteins, which generate an electrochemical proton gradient that produces energy in the form of adenosine triphosphate (ATP). Electron Transport Chain (ETC).)
    • Using a soft sleeping surface
    • Covering infant’s head
  • Child abuse Child abuse Child abuse is an act or failure to act that results in harm to a child’s health or development. The abuse encompasses neglect as well as physical, sexual, and emotional harm. Seen in all subsets of society, child abuse is a cause of significant morbidity and mortality in the pediatric population. Child Abuse
  • Family history Family History Adult Health Maintenance of SIDS
  • Overheating in a baby who sweats excessively

Pathophysiology

• Thought to be a sequential process:
  1. Initial state of hypoxia Hypoxia Sub-optimal oxygen levels in the ambient air of living organisms. Ischemic Cell Damage 
  2. Progressive bradycardia Bradycardia Bradyarrhythmia is a rhythm in which the heart rate is less than 60/min. Bradyarrhythmia can be physiologic, without symptoms or hemodynamic change. Pathologic bradyarrhythmia results in reduced cardiac output and hemodynamic instability causing syncope, dizziness, or dyspnea. Bradyarrhythmias
  3. Prolonged periods of apnea, and then suffocation
• May be interrupted by external stimuli that prompt the infant to breathe

Diagnosis and Management

Diagnosis

SIDS is a diagnosis of exclusion that can be assigned only after:

• A thorough examination of the scene and the circumstances surrounding the death
• An autopsy that does not determine a medical cause of death
  • Always indicated in cases without an identifiable cause of death (in many countries and jurisdictions, this is legally mandatory)
  • Autopsy findings in SIDS may include:
    • Well-fed infant in good condition
    • No obvious signs of agitation Agitation A feeling of restlessness associated with increased motor activity. This may occur as a manifestation of nervous system drug toxicity or other conditions. St. Louis Encephalitis Virus or trauma (injuries, petechiae Petechiae Primary Skin Lesions, ecchymosis Ecchymosis Extravasation of blood into the skin, resulting in a nonelevated, rounded or irregular, blue or purplish patch, larger than a petechia. Orbital Fractures)
    • Livor mortis found on the front of the body, but not on the face (due to prone position at the time of death)
    • Cyanotic lips Lips The lips are the soft and movable most external parts of the oral cavity. The blood supply of the lips originates from the external carotid artery, and the innervation is through cranial nerves. Lips and Tongue: Anatomy and nail beds

Management

The primary focus of management is providing an accurate post-mortem diagnosis as well as emotional and psychological support to the parents. Parents and family members should also be:

• Allowed to spend time with the deceased infant
• Offered grief counseling and closely monitored for signs of depression

Prevention

Parental education is key to preventing SIDS. As noted above, many of the risk factors are modifiable and can be prevented. Parental education includes:

• Encouraging regular Regular Insulin prenatal care Prenatal care Prenatal care is a systematic and periodic assessment of pregnant women during gestation to assure the best health outcome for the mother and her fetus. Prenatal care prevents and identifies maternal and fetal problems that adversely affect the pregnancy outcome. Prenatal Care during pregnancy Pregnancy The status during which female mammals carry their developing young (embryos or fetuses) in utero before birth, beginning from fertilization to birth. Pregnancy: Diagnosis, Physiology, and Care
• Encouraging cessation of tobacco and illicit drugs Illicit Drugs Drugs that are manufactured, obtained, or sold illegally. They include prescription drugs obtained or sold without prescription and non-prescription drugs. Illicit drugs are widely distributed, tend to be grossly impure and may cause unexpected toxicity. Delirium
• Safe sleeping practices
  • Infants should sleep Sleep A readily reversible suspension of sensorimotor interaction with the environment, usually associated with recumbency and immobility. Physiology of Sleep supine (on backs) until 1 year of age.
  • Use a firm mattress.
  • Maintain an uncluttered crib (no stuffed animals Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, animalia was one of the kingdoms. Under the modern three domain model, animalia represents one of the many groups in the domain eukaryota. Cell Types: Eukaryotic versus Prokaryotic, blankets, pillows, etc ETC The electron transport chain (ETC) sends electrons through a series of proteins, which generate an electrochemical proton gradient that produces energy in the form of adenosine triphosphate (ATP). Electron Transport Chain (ETC).).
  • Discourage co-sleeping (note that room-sharing is acceptable and may be a protective factor).
  • Discontinue swaddling when the infant can roll over.
  • Avoid overheating the infant/room.

Differential Diagnosis

The following conditions are natural causes of death to be distinguished from SIDS:

• Respiratory infections Infections Invasion of the host organism by microorganisms or their toxins or by parasites that can cause pathological conditions or diseases. Chronic Granulomatous Disease in children (e.g., bronchiolitis Bronchiolitis Inflammation of the bronchioles. Pediatric Chest Abnormalities, croup Croup Croup, also known as laryngotracheobronchitis, is a disease most commonly caused by a viral infection that leads to severe inflammation of the upper airway. It usually presents in children < 5 years of age. Patients develop a hoarse, "seal-like" barking cough and inspiratory stridor. Croup): can severely compromise oxygen intake and facilitate a state of apnea, with subsequent death if no intervention. 
• Long QT syndrome Long QT syndrome Long QT syndrome (LQTS) is a disorder of ventricular myocardial repolarization that produces QT prolongation on electrocardiogram (ECG). Long QT syndrome is associated with an increased risk of developing life-threatening cardiac arrhythmias, specifically torsades de pointes. Long QT Syndrome: a disorder of myocardial repolarization Repolarization Membrane Potential characterized by a prolonged QT interval QT interval Electrocardiogram (ECG) on electrocardiogram Electrocardiogram An electrocardiogram (ECG) is a graphic representation of the electrical activity of the heart plotted against time. Adhesive electrodes are affixed to the skin surface allowing measurement of cardiac impulses from many angles. The ECG provides 3-dimensional information about the conduction system of the heart, the myocardium, and other cardiac structures. Electrocardiogram (ECG); associated with an increased risk of developing life-threatening arrhythmias, most notably torsades de pointes Torsades de pointes A malignant form of polymorphic ventricular tachycardia that is characterized by heart rate between 200 and 250 beats per minute, and QRS complexes with changing amplitude and twisting of the points. The term also describes the syndrome of tachycardia with prolonged ventricular repolarization, long qt intervals exceeding 500 milliseconds or bradycardia. Torsades de pointes may be self-limited or may progress to ventricular fibrillation. Ventricular Tachycardia. Patients Patients Individuals participating in the health care system for the purpose of receiving therapeutic, diagnostic, or preventive procedures. Clinician–Patient Relationship may be relatively asymptomatic at the time of death.
• Inborn errors of fatty acid oxidation: Fatty acids Acids Chemical compounds which yield hydrogen ions or protons when dissolved in water, whose hydrogen can be replaced by metals or basic radicals, or which react with bases to form salts and water (neutralization). An extension of the term includes substances dissolved in media other than water. Acid-Base Balance are an important energy source for the infant, especially the newborn Newborn An infant during the first 28 days after birth. Physical Examination of the Newborn, as they are protective for brain Brain The part of central nervous system that is contained within the skull (cranium). Arising from the neural tube, the embryonic brain is comprised of three major parts including prosencephalon (the forebrain); mesencephalon (the midbrain); and rhombencephalon (the hindbrain). The developed brain consists of cerebrum; cerebellum; and other structures in the brain stem. Nervous System: Anatomy, Structure, and Classification tissue when glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance levels are low. Inborn errors of metabolism can cause a rapid depletion of energy stores.
• Reye’s syndrome: an acute hepatic decompensation seen in children who have been given aspirin Aspirin The prototypical analgesic used in the treatment of mild to moderate pain. It has anti-inflammatory and antipyretic properties and acts as an inhibitor of cyclooxygenase which results in the inhibition of the biosynthesis of prostaglandins. Aspirin also inhibits platelet aggregation and is used in the prevention of arterial and venous thrombosis. Nonsteroidal Antiinflammatory Drugs (NSAIDs) for temperature and symptom control during febrile illnesses.