Perspectives on population-based epidemiological studies of olfactory and taste impairment

Abstract

Epidemiological studies of the senses of olfaction (smell) and gustation (taste) are needed since impairments in these senses have important implications for health. Only a few attempts have been made to measure the prevalence of olfactory and gustatory or taste dysfunction, and many methodological challenges remain to be addressed. These challenges differ from those faced in studies based in the clinic or research laboratory. Epidemiological studies of smell and taste represent translational research, because they can be used to understand how findings from laboratory or clinical studies apply to the general population. This paper briefly reviews existing methods for "how" to measure smell and taste dysfunction and then illustrates findings based on prior epidemiological studies to indicate "why" we wish to measure smell and taste functioning in population-based samples. Self-reported information collected on smell and taste loss in a national sample, the 1994-1995 Disability Sample (phase I screening) of the National Health Interview Survey, is contrasted with results provided by an exam-based measure of olfactory impairment in an epidemiological study conducted in Beaver Dam, WI. The comparison of self-reported and exam-based measures of smell or taste loss leads to the question of how to best define smell or taste impairment in population samples, since unlike other sensory domains (namely, vision and hearing), there are no internationally accepted standards of impairment for the chemosenses. In addition to highlighting existing epidemiological studies, the current development of an NIH Toolbox of brief exam measures is described. Through this symposium, we hope to advance the nascent field of olfactory and taste epidemiology.

Figure 1

Self reported problems with sense of smell, based on questions in the U.S. National Health Interview Survey, Phase I Disability Supplement (NHIS-D), 1994–1995.

Figure 2

Prevalence of smell impairment based on the San Diego Odor Identification Test (SDOIT), as used in the Epidemiology of Hearing Loss Study (EHLS), a population-based study of sensory loss and aging in older adults in Beaver Dam, WI.

Figure 3

Comparison of odds ratios for selected multiple risk factors for smell impairment based on published findings from the Epidemiology of Hearing Loss Study (EHLS), a population-based study of sensory loss and aging in older adults in Beaver Dam, WI. The elliptical markers indicate odds ratio estimates for the risk factors and the shaded bars on either side represent 95% confidence intervals for the odds ratio estimates. All the variables were included in the multivariate logistic regression model, which means the odds ratio of each risk factor is adjusted for the effects of the other risk factors in the model.

Figure 4

Self reported problems with the sense of taste, based on questions in the U.S. National Health Interview Survey, Phase I Disability Supplement (NHIS-D), 1994–1995.

Figure 5

Global variation in sensitivity to the bitter taste of phenylthiocarbamide (PTC), or a related chemical compount, 6-n-propylthiouracil (PROP). The median and mid-range of percentages of non-tasters within each nationality or ethnic/racial group is plotted. The highest percentages of PTC non-tasters were reported for Australian Aborigines (plotted on the left side), while the lowest percentages of non-tasters were reported for Native American Indian groups (plotted on the right side). Data for this figure were extracted from a published table that summarized findings from tests conducted in more than 370 study samples worldwide, all published between 1934 and 1998.