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

• Published in: Journal of the International Neuropsychological Society Vol. 20; no. 2; pp. 209 - 217
• Main Authors: Stanciu, Ingrid, Larsson, Maria, Nordin, Steven, Adolfsson, Rolf, Nilsson, Lars-Göran, Olofsson, Jonas K.
• Format: Journal Article
• Language: English
• Published: New York, USA Cambridge University Press 01.02.2014
• Subjects: Aged; Aged, 80 and over; Alzheimer type dementia; Awareness; Community Health Planning; Dementia; Dementia - diagnosis; Disease Progression; Female; Humans; Logistic Models; Longitudinal Studies; Male; Memory; Mental Status Schedule; Middle Aged; Neuropsychological Tests; Olfaction; Olfaction Disorders - physiopathology; Predictive Value of Tests; Smell - physiology; Smell disorder; Vascular dementia; Vascular dementia; Smell disorder; Memory; Awareness; Olfaction; Alzheimer type dementia
• ISSN: 1355-6177; 1469-7661; 1469-7661
• DOI: 10.1017/S1355617713001409

We examined whether conversion to dementia can be predicted by self-reported olfactory impairment and/or by an inability to identify odors. Common forms of dementia involve an impaired sense of smell, and poor olfactory performance predicts cognitive decline among the elderly. We followed a sample of 1529 participants, who were within a normal range of overall cognitive function at baseline, over a 10-year period during which 159 were classified as having a dementia disorder. Dementia conversion was predicted from demographic variables, Mini-Mental State Examination score, and olfactory assessments. Self-reported olfactory impairment emerged as an independent predictor of dementia. After adjusting for effects of other predictors, individuals who rated their olfactory sensitivity as “worse than normal” were more likely to convert to dementia than those who reported normal olfactory sensitivity (odds ratio [OR] = 2.17; 95% confidence interval [CI] [1.40, 3.37]). Additionally, low scores on an odor identification test also predicted conversion to dementia (OR per 1 point increase = 0.89; 95% CI [0.81, 0.98]), but these two effects were additive. We suggest that assessing subjective olfactory complaints might supplement other assessments when evaluating the risk of conversion to dementia. Future studies should investigate which combination of olfactory assessments is most useful in predicting dementia conversion. (JINS, 2014, 20, 1–9)