Longitudinal telomere shortening and early Alzheimer's disease progression in adults with down syndrome.

Telomere shortening was shown to parallel Alzheimer's disease (AD) associated dementia. By using a dual PNA Probe system we have developed a practical method for comparing telomere length in T-lymphocyte interphases from individuals with Down syndrome (DS) with and without "mild cognitive impairment" (MCI-DS) and demonstrated that telomere length can serve as a valid biomarker for the onset of MCI-DS in this high-risk population. To verify progressive cognitive decline we have now examined sequential changes in telomere length in 10 adults with DS (N = 4 Female, N = 6 Male) developing MCI-DS. Cases were selected blind to telomere length from a sample of adults with DS previously enrolled in a prospective longitudinal study at 18-month intervals with clinical and telomere assessments: (1) MCI-DS group data were collected approximately three years prior to development of MCI-DS; (2) 18 months later; (3) when MCI-DS was first observed. These telomere measures were compared to those from another 10 adults with DS matched by sex and approximate age but without indications of MCI-DS (Controls). PNA (peptide nucleic acid) probes for telomeres together with a chromosome two centromere probe were used. Findings indicated telomere shortening over time for both Cases and Controls. Group differences emerged by 18-months prior to recognition of MCI-DS onset and completely non-overlapping distributions of telomere measures were observed by the time of MCI-DS onset. This study adds to accumulating evidence of the value of telomere length, as an early biomarker of AD progression in adults with Down syndrome.