| 1. |
- Olofsson, Jonas K., et al.
(author)
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Long-term episodic memory decline is associated with olfactory deficits only in carriers of ApoE-є4
- 2016
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In: Neuropsychologia. - : Elsevier BV. - 0028-3932 .- 1873-3514. ; 85, s. 1-9
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Journal article (peer-reviewed)abstract
- The ɛ4 allele of the Apolipoprotein E gene is a genetic risk factor for late-onset dementia of the Alzheimers' type (DAT), which is characterized by loss of both episodic memoryand olfactory functions. Little is known about the possible role of ɛ4 in the association between ongoing episodic memory decline and olfactory deficits in the general population, but such information is relevant in determining the relevance of olfaction as a marker of DAT risk. The present study was based on a large, population-based sample (n=1087, aged 45–90 years, of which 324 were ɛ4-carriers). Episodic memory change rates were established using data collected every 5 years for a 10–20 year interval leading up to an olfactory assessment using the Scandinavian Odor Identification Test at the last wave of data collection. Participants were classified according to whether or not their episodic memory ability declined more rapidly than the age-typical norm (by >1SD). Our main result is that only in ɛ4-carriers was episodic memory decline associated with odor identification impairment. In individuals without ɛ4, odor identification was unrelated to episodic memory decline status. Follow-up analyses indicated that this moderation by ɛ4 was due to the olfactory nature of the identification test, and that the effect was not caused by 63 individuals with dementia. Our results suggest that the ɛ4 determines the functional association between ongoing episodic memory decline and olfaction. These findings are consistent with the notion that ɛ4-carriers with DAT, compared to non-carriers, display a cortical atrophy pattern that is more focused on mediotemporal lobe regions supporting olfactory and episodic memory functions. Olfactory and memory assessments might provide complementary information on mediotemporal atrophy prior to clinical dementia onset, but the ɛ4 should be considered when using olfactory assessment as an early-stage indicator.
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| 2. |
- Ekström, Ingrid, et al.
(author)
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Smell Loss Predicts Mortality Risk Regardless of Dementia Conversion
- 2017
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In: Journal of The American Geriatrics Society. - : Wiley. - 0002-8614 .- 1532-5415. ; 65:6, s. 1238-1243
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Journal article (peer-reviewed)abstract
- ObjectivesTo determine whether dementia could explain the association between poor olfactory performance and mortality risk within a decade-long follow-up period.DesignProspective cohort study.SettingBetula Study, Umeå, Sweden.ParticipantsA population-based sample of adult participants without dementia at baseline aged 40 to 90 (N = 1,774).MeasurementsOlfactory 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.ResultsWithin 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.ConclusionPoor 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.
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| 3. |
- Larsson, Maria, et al.
(author)
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Loss of Olfactory Function Predicts Mortality Irrespective of Dementia Conversion : 10-year follow-up of an age-varied sample
- 2016
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In: Chemical Senses. - : Oxford University Press (OUP). - 0379-864X .- 1464-3553. ; 41:9, s. e111-e288
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Journal article (peer-reviewed)abstract
- The objective of this study was to examine the association between performance in odor identification and future mortality in a community cohort of adults aged between 40 and 90 years. We assessed olfactory performance with a 13-item-version of the Scandinavian Odor Identification Test (SOIT). The results showed that during follow-up (mean=9.4 years, standard deviation=2.23), 411 of 1774 (23.2%) participants died. In a Cox model, the association between higher SOIT score and mortality was highly significant (hazard ratio [HR]=0.74, per point interval, 95% confidence interval [CI]=0.71–0.77, p<0.001). The effect was attenuated, but remained significant after controlling for age, sex, education, and health and cognitive variables that were also associated with an increased risk of mortality (HR=0.92, 95% CI=0.87–0.97, p=0.001). Controlling for dementia conversion prior to death did not attenuate the association between SOIT score and mortality (HR=0.92, 95% CI=0.87–0.97, p=0.001). Similar results were obtained for olfactory sensitivity as assessed by self-report. Overall, the present findings show that poor odor identification performance is associated with an increased likelihood of future mortality in middle-aged and older adults, after controlling for social, cognitive, and medical risk factors. Most importantly, controlling for the development of dementia did not attenuate the association between odor identification and mortality, suggesting that olfactory decline might mark deteriorating health also irrespective of dementia.
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| 4. |
- Olofsson, Jonas K., et al.
(author)
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Odor Identification Deficit as a Predictor of Five-Year Global Cognitive Change : Interactive Effects with Age and ApoE-ε4
- 2009
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In: Behavior Genetics. - : Springer Netherlands. - 0001-8244 .- 1573-3297. ; 39:5, s. 496-503
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Journal article (peer-reviewed)abstract
- 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-ε4 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 ε4-carriers, who are at high risk of developing dementia.
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| 5. |
- Olofsson, Jonas K, 1965-, et al.
(author)
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Odor identification impairment in carriers of ApoE-ε4 is independent of clinical dementia
- 2010
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In: Neurobiology of Aging. - : Elsevier. - 0197-4580 .- 1558-1497. ; 31:4, s. 567-577
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Journal article (peer-reviewed)abstract
- 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.
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| 6. |
- Stanciu, Ingrid, et al.
(author)
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Olfactory Impairment and Subjective Olfactory Complaints Independently Predict Conversion to Dementia : A Longitudinal, Population-Based Study
- 2014
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In: Journal of the International Neuropsychological Society. - 1355-6177 .- 1469-7661. ; 20:2, s. 209-217
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Journal article (peer-reviewed)abstract
- 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)
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