Olfactory dysfunction as a predictor of neurodegenerative disease

Abstract

Olfactory dysfunction is present in patients diagnosed with Alzheimer's disease or idiopathic Parkinson's disease and can differentiate each of these disorders from related disorders with similar clinical presentations. The pathologic hallmarks of each disease are present in brain regions involved in processing olfactory input. Both the olfactory functional deficits and the corroborating pathologic lesions are present in asymptomatic subjects with increased risk of developing these diseases. Preclinical detection of neurodegenerative diseases is necessary to control their devastating effects on individuals and societies. We address whether olfactory dysfunction can be used to assess risk for developing Alzheimer's disease or Parkinson's disease in asymptomatic individuals. We argue that further characterization and a deeper understanding of olfactory deficits in these neurodegenerative diseases at the molecular, cellular, and systems levels will augment our acumen for preclinical detection and elucidate pathogenic mechanisms to guide the development of new therapeutic modalities.

Olfactory Impairment and Subjective Olfactory Complaints Independently Predict Conversion to Dementia: A Longitudinal, Population-Based Study

“…In conclusion, the results of this study support earlier findings suggesting that olfactory impairment is a pre-clinical marker for dementia (Albers, Tabert, & Devanand, 2006;Morgan, Nordin, & Murphy, 1995;Olofsson et al, 2009;Ponsen et al, 2004;Schubert et al, 2008). Most importantly, the results reveal that subjective olfactory impairment constitutes an early marker of an impending dementia.…”

The Predictive Role of Hyposmia in Alzheimer's Disease

“…The research on AD is now oriented to an early diagnosis which is essential before the development of the irreversible and typical changes due to AD. In AD patients, a reduced capacity for olfactory detection, discrimination and identification is usually found and confirmed by several studies (Mesholam et al, 1998;Hawkes, 2003;Kovacs, 2004;Albers et al, 2006;Westervelt et al, 2007). In this chapter we present a review on the predictive role of hyposmia in the early diagnosis of AD patients.…”

Odor identification and Alzheimer disease biomarkers in clinically normal elderly

“…31 Driven by the scenario that anti-AD therapies will likely prove most effective in individuals before the onset of symptoms, there is increased interest in simple, low-cost, noninvasive tests, such as the USPIT, capable of identifying atrisk individuals. One study that utilized the Brief Smell Identification Test (a 12-item test derived from and shown to correlate with the 40-item UPSIT) included a small group of individuals who died without evidence of cognitive impairment.…”