Telomere shortening in neurological disorders: an abundance of unanswered questions

• Leukocyte telomere length (LTL) typically shortens with increased age.
• Aging is a primary risk factor for neurodegenerative disease (ND).
• Evidence for LTL as a predictor of neuronal/glial telomere length and ND is mixed.
• We suggest possible explanations for variability in studies examining the LTL–ND relationship.

Telomeres, ribonucleoprotein complexes that cap eukaryotic chromosomes, typically shorten in leukocytes with aging. Aging is a primary risk factor for neurodegenerative disease (ND), and a common assumption has arisen that leukocyte telomere length (LTL) can serve as a predictor of neurological disease. However, the evidence for shorter LTL in Alzheimer's and Parkinson's patients is inconsistent. The diverse causes of telomere shortening may explain variability in LTL between studies and individuals. Additional research is needed to determine whether neuronal and glial telomeres shorten during aging and in neurodegenerative disorders, if and how LTL is related to brain cell telomere shortening, and whether telomere shortening plays a causal role in or exacerbates neurological disorders.