At what age do symptoms of Amyotrophic Lateral Sclerosis (ALS) typically onset?

Age of Onset for Amyotrophic Lateral Sclerosis (ALS)

The mean age of onset for Amyotrophic Lateral Sclerosis (ALS) is approximately 58-60 years, with most cases occurring between 40-70 years of age. 1

Epidemiology of ALS Onset

ALS onset follows specific age patterns:

• Mean age of onset: 58-60 years 1
• Age range distribution:
  • Most common: 40-70 years
  • Peak incidence: 60-70 years 2
  • Late-onset cases (>70 years): Increasingly recognized and potentially underdiagnosed 3
  • Early-onset cases (<40 years): Less common, often associated with genetic factors

Differences in Age of Onset by ALS Type

Sporadic ALS (90-95% of cases)

• Mean age of onset: Approximately 60 years 4
• Typically presents later than familial forms
• Respiratory failure typically occurs within 3-5 years of symptom onset for limb-onset cases 4

Familial ALS (5-10% of cases)

• Mean age of onset: Approximately 5.3 years younger than sporadic ALS 5
• This earlier onset is primarily due to genetic factors rather than ascertainment bias 5
• Genetic variants in sporadic cases also lead to earlier onset (2.9 years younger than non-genetic sporadic cases) 5

Onset Presentation and Prognosis

By Presentation Type

• Limb onset (65-75% of patients):

  • More common presentation
  • Typically has longer survival (3-5 years from onset) 4
  • Presents with focal muscle weakness and wasting in upper or lower limbs

• Bulbar onset (25-35% of patients):

  • Presents with dysarthria and dysphagia
  • Associated with shorter survival (2-3 years from onset) 4
  • More common in older patients
  • Often underdiagnosed in elderly populations 3

Prognostic Factors Related to Age

Age at onset is a significant prognostic factor:

• Older age at onset correlates with shorter survival 6
• Rapid symptom progression in the first 6 months after diagnosis is associated with poorer outcomes 6
• Bulbar onset, especially in older patients, carries worse prognosis 7

Clinical Implications

• ALS should be considered in the differential diagnosis for elderly patients presenting with dysphagia, frailty, or generalized weakness 3
• Late-onset ALS (>70 years) is more common than previously recognized and often missed in elderly patients 3
• Only 46% of patients referred with ALS symptoms had ALS considered by their referring physician, indicating potential diagnostic delays 3
• Videofluoroscopy is recommended at diagnosis for all ALS patients to detect early signs of dysphagia, even in those without obvious bulbar symptoms 2

Key Takeaway

While ALS can occur at any adult age, clinicians should maintain a high index of suspicion for ALS in patients in their 50s-60s presenting with progressive muscle weakness, especially when both upper and lower motor neuron signs are present. The disease is increasingly recognized in elderly populations where it may be misdiagnosed as age-related frailty or other conditions.