Age-related olfactory loss is associated with nigrostriatal dopaminergic degeneration

Objectives Mechanisms of age-associated olfactory loss are poorly understood. We investigated the relationship between severity of age-associated nigrostriatal dopaminergic denervation and olfactory performance in community-dwelling subjects.

Methods Community-dwelling subjects (n=85, 50F/35M, mean age 62.7±16.2, range 20-85) underwent brain dopamine transporter (DAT) [C-11]β-CFT PET imaging and olfactory assessment using the University of Pennsylvania Smell Identification Test (UPSIT). Subjects with clinical or DAT PET evidence of Parkinson disease were not eligible for the study.

Results Increased age was associated with lower olfactory scores (R=-0.48, P<0.0001) and lower striatal DAT binding (R=-0.81, P<0.0001). Higher striatal DAT binding correlated with better olfactory scores (R=0.53, P<0.0001) that remained significant (partial R=0.27, P=0.01) while accounting for the effect of age. There was no longer a significant age-related olfactory effect after accounting for striatal DAT losses (partial R=0.10, P=0.38).

Conclusions Age-associated nigrostriatal dopaminergic degeneration is a determinant of olfactory loss with aging and may indicate a novel pathobiological mechanism. It is plausible that more significant olfactory losses in some elderly may indicate the presence of neurodegenerative disorders, and may involve pathology including dopaminergic losses.

Research Support Department of Veterans Affairs