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Odor identification in aging and dementia: Influences of cognition and the ApoE gene
Umeå University, Faculty of Social Sciences, Psychology.
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Olfactory function is impaired in aging and dementia. The general aim of this thesis was to identify variables that predict olfactory function and dysfunction (assessed with an odor identification test) in middle-aged and elderly adults. The thesis investigated whether odor identification performance was associated with demographic variables, cognitive function, the ApoE gene, dementia, and other health-related variables. The ApoE-ε4 allele is associated with cognitive impairment and Alzheimer’s disease, the most common form of dementia. The studies included in this thesis used data from the Betula study, a large-scale, population-based prospective study on aging, memory, and health. Study 1 investigated demographic and cognitive predictors of odor identification ability in non-demented participants. The results showed that younger age, female sex, and high education contributed to better odor identification ability. Cognitive speed and vocabulary had a small additional influence. Study 2 included information about ApoE genotypes, dementia and other health-related variables. The results indicated that the ApoE-ε4 allele was associated with odor identification impairment among the elderly, but not middle-aged adults. Participants who were demented at the time of testing or became demented within five years after testing exhibited olfactory impairments. Interestingly, the age-related olfactory impairment in ε4-carriers was independent of clinical dementia within five years. In Study 3, decline in global cognitive status over a five-year test-retest interval was predicted in a sample of elderly participants. The major result was a three-way interaction reflecting that odor identification impairment, old age, in combination with the ε4 allele predicted a larger cognitive decline. However, odor identification impairment did not predict cognitive change in elderly who were non-carriers of the ε4 allele. Overall, the results indicate that odor identification impairment in elderly is related to ApoE-ε4, cognitive decline, and clinical and pre-clinical stages of dementia. Theoretical and practical implications of the results are discussed. Furthermore, it is proposed that in order to effectively predict clinical dementia or cognitive decline from olfactory assessment in the elderly, variables that mediate (e.g. neuropathology) or moderate (e.g. age) the associations between olfactory function, the ε4 allele, and dementia need to be further evaluated, preferably in studies using longitudinal assessment.

Place, publisher, year, edition, pages
Umeå: Psykologi , 2008. , 91 p.
Keyword [en]
Aging, olfaction, identification, dementia, Alzheimer, genetics, ApoE, population based, cognition, demographics
National Category
Psychology
Identifiers
URN: urn:nbn:se:umu:diva-1835ISBN: 9789172646520 (print)OAI: oai:DiVA.org:umu-1835DiVA: diva2:142153
Public defence
2008-10-10, Hörsal D, Samhällsvetarhuset, Umeå Universitet, Umeå, 10:15
Opponent
Supervisors
Available from: 2008-09-18 Created: 2008-09-18Bibliographically approved
List of papers
1. Demographic and cognitive predictors of cued odor identification performance: Evidence from a population-based sample
Open this publication in new window or tab >>Demographic and cognitive predictors of cued odor identification performance: Evidence from a population-based sample
2004 (English)In: Chemical Senses, Vol. 29, no 6, 547-554 p.Article in journal (Refereed) Published
Identifiers
urn:nbn:se:umu:diva-3449 (URN)
Available from: 2008-09-18 Created: 2008-09-18 Last updated: 2011-01-25Bibliographically approved
2. Odor identification impairment in carriers of ApoE-ε4 is independent of clinical dementia
Open this publication in new window or tab >>Odor identification impairment in carriers of ApoE-ε4 is independent of clinical dementia
Show others...
2010 (English)In: Neurobiology of Aging, ISSN 0197-4580, E-ISSN 1558-1497, Vol. 31, no 4, 567-577 p.Article in journal (Refereed) Published
Abstract [en]

The ApoE gene is expressed in olfactory brain structures and is believed to play a role in neuronal regenerative processes as well as in development of Alzheimer's disease (AD), the most common form of dementia. The ε4 allele has been reported to be associated with compromised odor identification ability in the elderly, and this deficit has been interpreted as a sign of pre-diagnostic AD. However, because it has not been demonstrated that the relationship between the ε4 allele and odor identification is mediated by dementia, it is possible that the ε4 allele may have an effect on odor identification over and above any effects of dementia. The present study investigated effects of ApoE-status on odor identification in a large, population-based sample (n = 1236) of adults (45–80 years), who were assessed for dementia at time of testing and 5 years later. The results showed that the ε4 allele was associated with an odor identification deficit among elderly participants (75–80). Critically, this effect remained after current and pre-diagnostic dementia, vocabulary, global cognitive status and health variables were partialled out. The present results suggest that the ApoE gene plays a role in olfactory functioning that is independent of dementia conversion within 5 years.

Place, publisher, year, edition, pages
Elsevier, 2010
Keyword
ApoE, odor identification, olfaction, aging, Alzheimer's disease
National Category
Psychology
Research subject
Psychology
Identifiers
urn:nbn:se:umu:diva-3450 (URN)10.1016/j.neurobiolaging.2008.05.019 (DOI)000276759700005 ()
Available from: 2008-09-18 Created: 2008-09-18 Last updated: 2017-12-14Bibliographically approved
3. Odor identification deficit as a predictor of five-year global cognitive change: Interactive effects with age and ApoE-ε4
Open this publication in new window or tab >>Odor identification deficit as a predictor of five-year global cognitive change: Interactive effects with age and ApoE-ε4
Show others...
2009 (English)In: Behavior Genetics, ISSN 0001-8244, E-ISSN 1573-3297, Vol. 39, no 5, 496-503 p.Article in journal (Refereed) Published
Abstract [en]

Olfactory impairments are present in common neurodegenerative disorders and predict conversion to dementia in non-demented individuals with cognitive impairment. In cognitively intact elderly, evidence is sparse regarding the role of olfactory deficits in predicting cognitive impairment. The present study investigated predictors of 5-year prospective decline in the Mini-Mental State Examination (MMSE) in a large (n = 501), population-based sample of elderly (65-90 years) individuals. All participants were genotyped for the ApoE gene, assessed for health factors, and were non-demented at the baseline assessment. After partialling out the influences of demographic and health-factors at baseline and dementia at follow-up, poor odor identification ability in combination with older age and the ApoE-epsilon4 allele predicted larger prospective global cognitive decline. This effect could not be produced by a vocabulary test. In sum, the findings suggest that an olfactory deficit can dissociate between benign and malign global cognitive development in non-demented, very old epsilon4-carriers, who are at high risk of developing dementia.

Place, publisher, year, edition, pages
Springer, 2009
Keyword
ApoE, Odor identification, Olfaction, Aging, Dementia
National Category
Psychology
Research subject
Psychology
Identifiers
urn:nbn:se:umu:diva-3451 (URN)10.1007/s10519-009-9289-5 (DOI)19633944 (PubMedID)
Available from: 2008-09-18 Created: 2008-09-18 Last updated: 2017-12-14Bibliographically approved

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