5. DETERMINE (13–15)
5.5 CHALLENGES FOR ASSESSING SENSORY FUNCTIONING IN OLDER PERSONS: COMPARISON OF TASTE AND SMELL
WITH OTHER SENSES
In current clinical practice, physicians and other medical personnel generally make diagnoses, treatment decisions, and clinical prognoses based on tests at a single point in time. Clinical research, however, suggests that tests obtained at a single time point are often inadequate to make a definitive diagnosis for a variety of
92 Schiffman
medical conditions. Sensory, sensorimotor, and psychological assessments(28)can be highly variable for a given individual over short time periods. This temporal variation for an individual relative to his/her own mean is called intra-individual variation.
A recent study emphasizes the difficulty of relying on a single assessment of sensory function at one time point in older individuals. Schiffman (9) evaluated sensory performance (all five sensory modalities as well as cognition) concomitantly in three groups of non-demented older subjects including coronary artery bypass surgery patients, patients with cardiovascular conditions but with no history of surgery, Table 5.2
Sensory (and cognitive) tests ranked by percent of non-medicated older persons who per- formed best on the first test of a series of four repeated tests
Test
modality Specific test type
Percentage of persons who performed best on the first
of four repetitions
Cognitive Immediate Recall1 11.3
Cognitive Delayed Recall2 18.3
Touch Tactile special sensitivity thresholds3 19.0
Cognitive Symbol Digit Modalities Test4 19.7
Taste Sucrose detection threshold5 26.1
Taste Sucrose (sweet) recognition threshold5 26.8
Taste Quinine HCl detection threshold5 26.8
Taste NaCl detection threshold5 28.2
Hearing Thresholds (in decibels) at 6000 Hz6 29.6 Taste NaCl (salty) recognition threshold5 31.7 Taste Quinine HCl (bitter) recognition
threshold5
31.7 Hearing Thresholds (in decibels) at 8000 Hz6 33.1 Vision Contrast Sensitivity Row D (somewhat
difficult)7
38.7 Cognitive Mini Mental Status Examination
(MMSE)8
39.4
Smell Smell identification9 40.8
Smell Smell Memory10 40.8
Vision Contrast Sensitivity Row E (most difficult)7
40.8
Smell Butanol detection threshold11 41.5
Hearing Thresholds (in decibels) at 4000 Hz6 42.3 Vision Contrast Sensitivity Row A (easiest)7 43.0 Hearing Thresholds (in decibels) at 500 Hz6 43.7 Hearing Thresholds (in decibels) at 2000 Hz6 50.0 Vision Contrast Sensitivity Row C (moderate
difficulty)7
50.7
(continued )
Chapter 5/ Sensory Impairment 93
Table 5.2 (continued)
Hearing Thresholds (in decibels) at 1000 Hz6 50.7
Vision Near Vision12 52.1
Vision
Contrast Sensitivity Row B (relatively easy)7
53.5
1Immediate recall: Subjects read aloud a list of 13 word pairs, with each pair presented at 3 s intervals. After a second presentation of these same word pairs, subjects were given the cue words (first words of each pair) on a page, but the target words (second words of each pair) were absent (blank line). Subjects were asked to write on the blank lines as many of the pair-associated words as they could remember. The maximum correct score attainable was 13.
2Delayed recall: Same as immediate recall but after a 5–10 min delay.
3Tactile spatial sensitivity thresholds: Cutaneous spatial resolution on the fingertip of the index finger was measured by assessing orientation of spatial gratings (JVP Domes, Stoelting Company, Wood Dale, IL)(29). The score is the narrowest spatial resolution that the subject can detect in millimeters (mm).
4The Symbol Digit Modalities Test (SDMT) evaluates processing speed (30). Subjects were presented with a key that pairs each digit from 1 to 9 with a specific geometric symbol. The subject was then instructed to fill in rows of blank boxes with the digits that correspond to the symbols presented directly above the boxes. Subjects were allotted 90 s to write the digits in as many possible consecutive boxes in a row without skipping any items.
5The detection threshold is the concentration at which the subject correctly distinguished the tastant as stronger than a water control. The recognition threshold (recognition threshold) is the concentration at which the subject correctly identified the taste as salty (NaCl), sweet (sucrose), or bitter (quinine HCl).
6Thresholds (in decibels) for six pure tones (500, 1000, 2000, 4000, 6000, and 8000 Hz) were determined for each ear using the Maico 25 portable air conduction audiometer and an audiocup headset (Eden Prairie, MN). A total score was computed by adding the decibels required to reach threshold at each of the six pure tones and dividing by six. Lower total scores indicated better performances.
7Contrast sensitivity refers to the visual ability to distinguish between an object and its back- ground and is considered a more sensitive measure of visual status than standard visual acuity measures. The Functional Acuity Contrast Test (FACT) Chart (Stereo Optical Co., Chicago, IL) was used to measure contrast sensitivity. Subjects reported the orientation (up, left, or right) of gray sine-wave grating lines at progressively decreasing contrast. The FACT chart tests five spatial frequencies in rows labeled A (easiest), B, C, D, and E (most difficult).
8The MMSE is a brief screening instrument that assesses orientation and cognitive status in adults(31).
9Subjects were asked to identify 12 odors with the use of a list of 27 names of odorous substances. The test score was the total number correct out of 12 target substances.
10Smell memory was assessed for four odorants using procedures described by Schiffman et al.(17).
Subjects were instructed to sniff one bottle containing the target odor and then try to remember it. Subjects then counted backward by threes for 7 s from a number given by the examiner. Subjects were sequentially presented with a set of the four odorants and were asked to identify which of the four had the odor that they were asked to remember. Each odor was presented twice, for a total of eight trials, and scoring was based on the total number of correctly remembered smells, with eight as the maximum score.
11The butanol detection threshold was the concentration at which the subject correctly distinguished the odor as stronger than a water control. The threshold is expressed as concentration (% v/v) of 1-butanol in deionized water.
12Near visual acuity for each eye was assessed using a Rosenbaum Pocket Vision Screening Chart (Western Ophthalmics Corporation, Lynnwood, WA), with the subject wearing his/her personal visual correction when needed. The near visual acuity score was determined to be the lowest line at which a subject could correctly identify at least half the numbers or symbols. Mean score is the denominator of the distance equivalent, e.g., 20/20, 20/30, i.e., 20/36.9 is worse than 20/33.1.
94 Schiffman
and healthy non-medicated age-matched controls. All subjects were tested three times over a 2-month period in order to investigate and compare short-term intra-indivi- dual fluctuation or lability of the five senses and cognition over a short time period when little change in perception was expected. The non-medicated control group was also tested a fourth time four months after the 2-month testing in triplicate.
The main findings of the study were as follows. First, the intra-individual variability was extensive for all three groups although it was significantly greater for the coronary artery bypass surgery patients than for the other two groups that were statistically equivalent. Second, the greatest individual variability (as well as magnitude of sensory losses for the coronary bypass patients) was for taste and smell thresholds. Third, correlations among the tests of different modalities revealed that performance in one sensory modality does not necessarily correlate with performance in another modality. Fourth, the initial or first sensory (and cognitive) assessment of the repetitions seldom provided the best performance for the majority of the tests (see Table 5.2 for data on the non-medicated cohort). The variability for the medicated (but not surgical) patients was similar to the non- medicated cohort, but the surgical patients showed significantly more fluctuation (9). This finding is important because it emphasizes that sensory sensitivity varies from day to day, and multiple assessments of the senses are necessary to establish the range (maximum to minimum) of sensory performance.