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Olfactory thresholds of the U.S. Population of home-dwelling older adults: development and validation of a short, reliable measure.

Kern DW, Schumm LP, Wroblewski KE, Pinto JM, Hummel T, McClintock MK - PLoS ONE (2015)

Bottom Line: Simulated subjects were assigned n-butanol thresholds drawn from the estimated normosmic distribution and based on these and the model, we simulated administration of both the staircase and constant stimuli methods.Our results replicate both the correlation between the two methods and their reliability as previously reported by studies using human subjects.Thus, testing with a fast, 6-item constant stimuli protocol is informative, and permits olfactory testing in previously inaccessible research settings.

View Article: PubMed Central - PubMed

Affiliation: Institute for Mind and Biology and Department of Comparative Human Development, The University of Chicago, Chicago, IL, United States of America.

ABSTRACT
Current methods of olfactory sensitivity testing are logistically challenging and therefore infeasible for use in in-home surveys and other field settings. We developed a fast, easy and reliable method of assessing olfactory thresholds, and used it in the first study of olfactory sensitivity in a nationally representative sample of U.S. home-dwelling older adults. We validated our method via computer simulation together with a model estimated from 590 normosmics. Simulated subjects were assigned n-butanol thresholds drawn from the estimated normosmic distribution and based on these and the model, we simulated administration of both the staircase and constant stimuli methods. Our results replicate both the correlation between the two methods and their reliability as previously reported by studies using human subjects. Further simulations evaluated the reliability of different constant stimuli protocols, varying both the range of dilutions and number of stimuli (6-16). Six appropriately chosen dilutions were sufficient for good reliability (0.67) in normosmic subjects. Finally, we applied our method to design a 5-minute, in-home assessment of older adults (National Social Life, Health and Aging Project, or NSHAP), which had comparable reliability (0.56), despite many subjects having estimated thresholds above the strongest dilution. Thus, testing with a fast, 6-item constant stimuli protocol is informative, and permits olfactory testing in previously inaccessible research settings.

No MeSH data available.


Distribution of Thresholds for Normosmics and NSHAP.Threshold distributions used for simulations, based on model-estimated distributions for the 590 normosmic sample and the NSHAP Wave 2 sample (n = 2,207) of older adults. The means and standard deviations for both samples are as estimated by the IRT model; the Normal distribution for the NSHAP sample has been replaced by a gamma distribution with identical mean and standard deviation, to more closely approximate the likely distribution of thresholds in the population.
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pone.0118589.g003: Distribution of Thresholds for Normosmics and NSHAP.Threshold distributions used for simulations, based on model-estimated distributions for the 590 normosmic sample and the NSHAP Wave 2 sample (n = 2,207) of older adults. The means and standard deviations for both samples are as estimated by the IRT model; the Normal distribution for the NSHAP sample has been replaced by a gamma distribution with identical mean and standard deviation, to more closely approximate the likely distribution of thresholds in the population.

Mentions: Given that thresholds of 4% n-butanol or greater are often considered indicative of functional anosmia, we substituted a three-parameter gamma distribution with shape parameter 3.35, scale parameter 1.61 and location parameter-3 (Fig. 3). This distribution has the same mean and standard deviation as the estimated Normal distribution, but its positively-skewed shape is more likely to match the distribution of actual thresholds in this population. In particular, according to this distribution, 9% of the population has a threshold of 16% n-butanol or greater, only 1% has a threshold of 32% or greater, and none has a threshold of 64% or greater. The estimated slope parameter of 0.76 was used to simulate individual responses. A sample size of 2,000 respondents was used to approximate the NSHAP sample, and as before, 500 replications per condition were performed.


Olfactory thresholds of the U.S. Population of home-dwelling older adults: development and validation of a short, reliable measure.

Kern DW, Schumm LP, Wroblewski KE, Pinto JM, Hummel T, McClintock MK - PLoS ONE (2015)

Distribution of Thresholds for Normosmics and NSHAP.Threshold distributions used for simulations, based on model-estimated distributions for the 590 normosmic sample and the NSHAP Wave 2 sample (n = 2,207) of older adults. The means and standard deviations for both samples are as estimated by the IRT model; the Normal distribution for the NSHAP sample has been replaced by a gamma distribution with identical mean and standard deviation, to more closely approximate the likely distribution of thresholds in the population.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4359123&req=5

pone.0118589.g003: Distribution of Thresholds for Normosmics and NSHAP.Threshold distributions used for simulations, based on model-estimated distributions for the 590 normosmic sample and the NSHAP Wave 2 sample (n = 2,207) of older adults. The means and standard deviations for both samples are as estimated by the IRT model; the Normal distribution for the NSHAP sample has been replaced by a gamma distribution with identical mean and standard deviation, to more closely approximate the likely distribution of thresholds in the population.
Mentions: Given that thresholds of 4% n-butanol or greater are often considered indicative of functional anosmia, we substituted a three-parameter gamma distribution with shape parameter 3.35, scale parameter 1.61 and location parameter-3 (Fig. 3). This distribution has the same mean and standard deviation as the estimated Normal distribution, but its positively-skewed shape is more likely to match the distribution of actual thresholds in this population. In particular, according to this distribution, 9% of the population has a threshold of 16% n-butanol or greater, only 1% has a threshold of 32% or greater, and none has a threshold of 64% or greater. The estimated slope parameter of 0.76 was used to simulate individual responses. A sample size of 2,000 respondents was used to approximate the NSHAP sample, and as before, 500 replications per condition were performed.

Bottom Line: Simulated subjects were assigned n-butanol thresholds drawn from the estimated normosmic distribution and based on these and the model, we simulated administration of both the staircase and constant stimuli methods.Our results replicate both the correlation between the two methods and their reliability as previously reported by studies using human subjects.Thus, testing with a fast, 6-item constant stimuli protocol is informative, and permits olfactory testing in previously inaccessible research settings.

View Article: PubMed Central - PubMed

Affiliation: Institute for Mind and Biology and Department of Comparative Human Development, The University of Chicago, Chicago, IL, United States of America.

ABSTRACT
Current methods of olfactory sensitivity testing are logistically challenging and therefore infeasible for use in in-home surveys and other field settings. We developed a fast, easy and reliable method of assessing olfactory thresholds, and used it in the first study of olfactory sensitivity in a nationally representative sample of U.S. home-dwelling older adults. We validated our method via computer simulation together with a model estimated from 590 normosmics. Simulated subjects were assigned n-butanol thresholds drawn from the estimated normosmic distribution and based on these and the model, we simulated administration of both the staircase and constant stimuli methods. Our results replicate both the correlation between the two methods and their reliability as previously reported by studies using human subjects. Further simulations evaluated the reliability of different constant stimuli protocols, varying both the range of dilutions and number of stimuli (6-16). Six appropriately chosen dilutions were sufficient for good reliability (0.67) in normosmic subjects. Finally, we applied our method to design a 5-minute, in-home assessment of older adults (National Social Life, Health and Aging Project, or NSHAP), which had comparable reliability (0.56), despite many subjects having estimated thresholds above the strongest dilution. Thus, testing with a fast, 6-item constant stimuli protocol is informative, and permits olfactory testing in previously inaccessible research settings.

No MeSH data available.