Aging and Down Syndrome

The initial clinical description of Down syndrome (DS) was made by Down in 1866 [1] and identified as trisomy of chromosome 21 by Lejeune et al. in 1959 [2]. DS, or trisomy 21, is one of the most common causes of intellectual disability (ID), and recent national prevalence estimates suggest that 14.47 per 10,000 live births are infants with DS, leading to an average of 6037 annual DS births [3]. This represents an increase from previous prevalence rates. Characteristic physical features, deficits in the immune and endocrine systems, and delayed cognitive development [4] can be present in children with DS. Improvements in medical care for children and adults with DS have led to significant extensions in lifespan and enhanced quality of life. As a consequence, up to 35 years of age, mortality rates are comparable in adults with DS to individuals with ID from other causes. However, after age 35, mortality rates double every 6.4 years in DS, as compared to 9.6 years for people without DS [5], and the currently estimated life expectancy of a 1-year-old child with DS is between 43 and 55 years (depending on the level of disability). Although longevity in adults with DS has been increasing progressively, these increases have been substantially lower for some minority groups [6, 7]. Further, as described by L. Thorpe et al., adults with DS are still disadvantaged compared to adults with other types of ID in terms of mortality rate, with multiple comorbidities being of significant concern (e.g., depression, seizures). Significant contributors to quality of life in aging individuals with DS also include gait disturbances (B. A. Smith et al.) and ophthalmic disorders (e.g., S. J. Krinsky-MC. Hale et al.), both of which increase with age.