What is the life expectancy for individuals with autism spectrum disorder, stratified by severity, intellectual disability, and gender?

Life Expectancy in Autism Spectrum Disorder

Individuals with autism spectrum disorder experience reduced life expectancy compared to the general population, with the magnitude of reduction varying substantially by presence of intellectual disability and gender: autistic men without intellectual disability lose approximately 6 years of life, autistic women without intellectual disability lose approximately 6.5 years, autistic men with intellectual disability lose approximately 7 years, and autistic women with intellectual disability lose approximately 15 years. 1

Mortality Rates and Life Expectancy Data

The most recent and comprehensive UK cohort study (2024) provides the highest quality estimates available, though these figures likely overestimate mortality risk for the broader autistic population due to significant diagnostic ascertainment bias 1:

Without Intellectual Disability

• Men: 6.14 years of life lost (95% CI: 2.84-9.07 years) 1
• Women: 6.45 years of life lost (95% CI: 1.37-11.58 years) 1
• Standardized mortality ratio: 1.71 times the rate of non-autistic individuals 1

With Intellectual Disability

• Men: 7.28 years of life lost (95% CI: 3.78-10.27 years) 1
• Women: 14.59 years of life lost (95% CI: 9.45-19.02 years) 1
• Standardized mortality ratio: 2.83 times the rate of non-autistic individuals 1

Critical Interpretation: The Diagnostic Ascertainment Problem

These estimates must be interpreted with extreme caution because approximately 90% of autistic adults remain undiagnosed, meaning the studied population represents only those with the greatest support needs and most severe co-occurring conditions. 1 The widely cited statistic that autistic people live 16 years less on average is likely incorrect and represents a significant overestimate of mortality risk for the general autistic population 1.

The diagnosed cohort studied consists disproportionately of individuals with:

• Greater-than-average support needs 1
• More co-occurring health conditions 1
• Higher functional impairment 1

Gender-Specific Mortality Patterns

The substantially larger reduction in life expectancy for women with autism and intellectual disability (14.59 years vs. 7.28 years for men) likely reflects disproportionate underdiagnosis of autism and/or intellectual disability in women rather than true biological vulnerability. 1 This aligns with evidence that females with ASD require more severe impairment to reach diagnostic attention, as their behaviors are typically less disruptive and overt 2.

Women with ASD show:

• Greater cognitive impairment at diagnosis, with male:female ratios approaching 1:1 in severely intellectually disabled populations 2
• More internalizing symptoms (anxiety, depression) rather than externalizing behaviors 2
• Evidence of a "female protective effect" requiring higher genetic load to manifest clinical ASD 2

Predictors of Mortality Risk

A 20-year longitudinal study identified specific predictors of premature death in autistic individuals 3:

Functional and Social Factors:

• Early childhood impairments in social reciprocity predict mortality even after controlling for age and health status 3
• High levels of functional impairment at baseline independently predict mortality 3
• Average age at death in this cohort was 39 years, with 6.4% mortality over 20 years 3

Causes of Death:

• Chronic conditions (cancer, heart disease) 3
• Accidents (choking on food, accidental poisoning) 3
• Health complications from medication side effects 3

Severity Stratification and Functional Outcomes

Cognitive level is the primary driver of mortality risk and functional outcomes, outweighing core social-communication deficits themselves. 4, 5

Intellectual Disability Distribution in ASD:

• 30% have co-occurring intellectual disability overall 4, 5
• 50% of those with intellectual disability have severe to profound impairment (IQ <35-40) 5
• 35% have mild to moderate intellectual disability (IQ 40-70) 5
• 15-20% have normal-range IQ (≥70) 5

Functional Outcomes Across the Lifespan:

• More than 50% of young adults with ASD have no participation in postsecondary education or employment within 2 years after high school 4, 6
• Approximately 90% have at least one additional medical or mental health condition requiring ongoing management 4, 5
• Presence of functional speech by age 5 is the strongest predictor of favorable long-term outcome 4

Clinical Pitfalls to Avoid

Do not counsel families using the "16-year reduction" statistic, as this represents exposure misclassification bias from studying only diagnosed individuals who comprise less than 10% of the autistic population. 1 The true reduction in life expectancy for the broader autistic population is likely substantially smaller than published estimates suggest 1.

Do not assume that ASD itself is a degenerative condition contributing to mortality—it is a static neurodevelopmental disorder without progressive neurological deterioration. 4 Premature mortality stems from co-occurring medical conditions, accidents, inadequate healthcare access, and complications of treatment rather than the autism itself 3, 7.

Recognize that individuals with greater functional impairment and intellectual disability face compounded mortality risk, with lifetime costs estimated at $2.4 million compared to $1.4 million without intellectual disability. 5, 6