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Smell Loss Predicts Mortality Risk Regardless of Dementia Conversion
Stockholm University, Faculty of Social Sciences, Department of Psychology, Perception and psychophysics.
Stockholm University, Faculty of Social Sciences, Department of Psychology, Perception and psychophysics.
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Number of Authors: 8
2017 (English)In: Journal of The American Geriatrics Society, ISSN 0002-8614, E-ISSN 1532-5415, Vol. 65, no 6, p. 1238-1243Article in journal (Refereed) Published
Abstract [en]

Objectives

To determine whether dementia could explain the association between poor olfactory performance and mortality risk within a decade-long follow-up period.

Design

Prospective cohort study.

Setting

Betula Study, Umeå, Sweden.

Participants

A population-based sample of adult participants without dementia at baseline aged 40 to 90 (N = 1,774).

Measurements

Olfactory performance using the Scandinavian Odor-Identification Test (SOIT) and self-reported olfactory function; several social, cognitive, and medical risk factors at baseline; and incident dementia during the following decade.

Results

Within the 10-year follow-up, 411 of 1,774 (23.2%) participants had died. In a Cox model, the association between higher SOIT score and lower mortality was significant (hazard ratio (HR) = 0.74 per point interval, 95% confidence interval (CI) = 0.71-0.77, P < .001). The effect was attenuated, but remained significant, after controlling for age, sex, education, and health-related and cognitive variables (HR = 0.92, 95% CI = 0.87-0.97, P = .001). The association between SOIT score and mortality was retained after controlling for dementia conversion before death (HR = 0.92, 95% CI = 0.87-0.97, P = .001). Similar results were obtained for self-reported olfactory dysfunction.

Conclusion

Poor odor identification and poor self-reported olfactory function are associated with greater likelihood of future mortality. Dementia does not attenuate the association between olfactory loss and mortality, suggesting that olfactory loss might mark deteriorating health, irrespective of dementia.

Place, publisher, year, edition, pages
2017. Vol. 65, no 6, p. 1238-1243
Keyword [en]
olfaction disorders, smell, Alzheimer disease, mortality, longitudinal studies
National Category
Psychology Geriatrics
Research subject
Psychology
Identifiers
URN: urn:nbn:se:su:diva-145242DOI: 10.1111/jgs.14770ISI: 000403894000021PubMedID: 28326534OAI: oai:DiVA.org:su-145242DiVA, id: diva2:1128670
Available from: 2017-07-27 Created: 2017-07-27 Last updated: 2018-04-18Bibliographically approved
In thesis
1. Human olfaction: Associations with longitudinal assessment of episodic memory, dementia, and mortality risk
Open this publication in new window or tab >>Human olfaction: Associations with longitudinal assessment of episodic memory, dementia, and mortality risk
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

A declining sense of smell is a common feature in older age. Above and beyond diminished smelling capacity due to normal processes of human aging, impairments in olfactory function have also been linked to numerous ill-health related outcomes, such as cognitive dysfunctions, dementia pathology and even an increased risk of death. Based on population-based data from the Swedish Betula Prospective Cohort Study, the aim of this thesis was to further our understanding regarding the role of olfaction in long-term memory decline, dementia, and mortality. Furthermore, this thesis investigated the predictive utility of self-reported olfactory dysfunction for assessing the risk of conversion to later dementia and to mortality, as well as the predictive utility of long-term subjective olfactory decline for an actual long-term decline in odor function. Study I explored associations of olfactory deficits with memory decline and found that impairments in an odor identification test were related to an ongoing and long-term decline in episodic memory only in carriers of the e4 allele of the Apolipoprotein E, a genetic risk factor for Alzheimer’s disease. Study II investigated the predictive utility of olfactory ability for conversion to common forms of dementia in participants with intact baseline cognition during a follow-up time-span of 10 years. The results showed that lower odor identification scores, as well as subjectively assessed odor impairment, were associated with an increased risk for dementia conversion, and that the effects of objective and subjective odor function were cumulative. Study III investigated whether olfactory ability could predict mortality and showed that lower odor identification scores, as well as subjective odor impairments, were associated with an elevated risk of death within a follow-up time-span of approximately 10 years. Crucially, this effect could not be explained by dementia conversion prior to death. Study IV showed that a subjectively assessed long-term and ongoing olfactory decline was predictive of an objectively assessed long-term and ongoing decline in odor function. Subjective olfactory impairments might thus be indicative of an actual olfactory decline in older adults. Overall, the findings of this thesis indicate that sense of smell is closely related to processes of memory decline and dementia as well as mortality in older adults. Furthermore, the results of these investigations shed a new light on the role of subjectively experienced olfactory decline, which might reflect an actual intra-individual change in olfactory ability in older adults.

Place, publisher, year, edition, pages
Stockholm: Department of Psychology, Stockholm University, 2018. p. 147
Keyword
olfaction, odor identification, self-assessments, aging, episodic memory, ApoE, dementia, Alzheimer’s disease, vascular dementia, mortality, cohort study, population-based.
National Category
Psychology
Research subject
Psychology
Identifiers
urn:nbn:se:su:diva-154414 (URN)978-91-7797-220-4 (ISBN)978-91-7797-221-1 (ISBN)
Public defence
2018-06-08, David Magnussonsalen (U31), Frescati Hagväg 8, Stockholm, 09:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Submitted.

Available from: 2018-05-16 Created: 2018-04-17 Last updated: 2018-05-09Bibliographically approved

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