Abstract
Objective
To investigate olfactory function in elderly subjects requiring nursing care to clarify its association with appetite and nutritional status.
Setting
Facility for the elderly requiring nursing care. Participants: The subjects were 158 elderly people requiring nursing care and 37 elderly people not requiring nursing care.
Measurements
Experiment I: Olfactory function and factors (cognitive function, appetite, and nutritional status) that may be associated with it were compared between the elderly subjects requiring nursing care and those not requiring nursing care using covariance analysis in consideration of age. For evaluation, the OSIT-J was used for olfactory function, the HDS-R for cognitive function, the CNAQ for appetite, and BMI for nutritional status. Experiment II: The subjects were the same elderly subjects requiring nursing care in Experiment I, and food intake was surveyed in addition to the OSIT-J, HDS-R, CNAQ, and BMI. A univariate linear regression analysis was performed with OSIT-J as the response variable, and age, HDS-R, CNAQ, BMI, and food intake as the explanatory variables.
Results
Experiment I: On covariance analysis, the OSIT-J score was significantly lower for the elderly subjects requiring nursing care than for those not requiring nursing care (p<0.01). The mean score was 8 or lower in both groups, demonstrating lower olfactory function in both groups. Regarding factors that may be associated with olfactory function, a significant difference was noted in the HDS-R (p<0.01), confirming significantly lower cognitive function in the elderly subjects requiring nursing care. No significant difference was noted in the CNAQ or BMI. Experiment II: On a univariate linear regression analysis, an association with the OSIT-J was noted for age and HDS-R. Age was inversely correlated and the HDS-R was positively correlated. Factors associated with lower olfactory function in the elderly subjects requiring nursing were age and cognitive function, whereas appetite, nutritional status, and food intake were not associated.
Conclusion
Olfactory function in elderly subjects requiring nursing care was poorer than that in those not requiring nursing care, suggesting that aging and cognitive decline are associated with lower olfactory function. In addition, no association of lower olfactory function with appetite, nutritional status, or food intake was noted in the elderly subjects requiring nursing care.
Key words: Olfactory function, appetite, nutritional status, elderly requiring nursing care
Introduction
Aging has progressed and undernutrition of the elderly due to loss of appetite is problematic in Japan. Undernutrition of the elderly requiring support and nursing is a serious problem (1) because it negatively affects the life prognosis (2). Therefore, measures to improve nutrition are necessary such as use of dietary supplements, meal planning, and aids to maintain and improve appetite. Appetite is essential for spontaneous ingestion of nutrients, and it is regulated by not only intrinsic factors, such as stimulation of the appetite center by hormones, but also extrinsic factors. Smell is an extrinsic factor affected by odor molecules, which are volatile chemical substances. Odor molecules are received by nerve cells of the olfactory epithelium, which is a sensory organ, and smells are recognized through transmission of the information from the olfactory bulb to the brain region through neural circuits, including the olfactory cortex. Smells are recognized in brain regions including the amygdala, which controls emotions and feeling, and the prefrontal cortex, which is responsible for value judgment, motivating ‘eating' and ‘wanting to eat' (3). However, the sense of smell and olfactory function begin to decline with age in the 50s (4), and are further affected by different diseases. Moreover, it has been reported that the decline in olfactory function is associated with appetite (5, 6, 7). These findings suggest that elderly patients requiring nursing care are not able to readily smell meals due to the decline in olfactory function, and consequently lose their appetite. This highlights the need for measures that focus on olfactory function to improve the loss of appetite and undernutrition in elderly patients. The objective of this study was to assess olfactory function in the elderly requiring nursing care, and clarify whether their olfactory function is associated with appetite and nutritional status.
Methods
In Experiment I, to examine whether olfactory function is poorer in the elderly requiring nursing care, it was compared between elderly subjects requiring and not requiring nursing care. In Experiment II, a univariate linear regression analysis was performed to assess whether olfactory function is associated with age, cognitive function, appetite, nutritional status, and food intake of the elderly requiring nursing care. This study was performed after approval by the ethics committees of the School & Graduate School of Dentistry, Osaka University, and Osaka University Dental Hospital (approval number: H29-E24-1).
Experiment I
Subjects
The subjects were selected from 189 elderly persons aged 65 years or older requiring nursing care in facilities, excluding those with nasal disease (chronic sinusitis, allergic rhinitis, nasal septum deviation, or cold) or a score of 10 or lower on the Hasegawa dementia rating scale-revised (HDS-R)(The score is 0–30). Subjects with nasal disease were excluded because nasal diseases may influence the results as a local factor by impairing the sense of smell (8). The cut-off value of the HDS-R was set at 10 because a score of 11 or higher is classified as moderate dementia and persons with a score of 11 or higher can live with assistance, although independence is difficult and they can judge their own subjective condition (9). In addition, persons with a past medical history of serious heart failure causing edema were excluded because of the use of BMI. As a result, the number of subjects was 158, the mean age was 84.4±7.1 years old (65–102 years old), and the mean care need level was 2.1. The care need level represents the degree of necessity of nursing insurance service in Japan. It is classified based on the time that nursing is required per day into 7 levels: support need levels 1 and 2, representing conditions with partial interference in daily life, and care need levels 1–5, representing conditions requiring assistance for some or all activities of daily life. The control group comprised 37 elderly subjects aged 65 years or older requiring no nursing care and not registered as in need of nursing (mean age: 81.2±5.9 years old (range: 68–90 years old)).
Survey items
Olfactory function and factors that may be associated with it (cognitive function, appetite, and nutritional status) were surveyed.
Olfactory function
The sense of smell is generated by receiving chemical substances at receptors and the action of the sensory organ is termed olfactory function. There are three main types of tests to evaluate olfactory function: 1) the identification capacity test used to evaluate the ability to identify the smell , 2) the threshold test used to evaluate the minimum concentration required to recognize smell, and 3) the discrimination ability test used to evaluate changes in the minimum concentration required to recognize changes in the sensory intensity and quality. Of these tests, the identification capacity test is the most frequently used olfactory function test (10).
To survey olfactory function, the Odor Stick Identification Test for Japanese (OSIT-J) (Daiichi Yakuhin Sangyo Co., Ltd., Tokyo, Japan) (11) was used. The OSIT-J is a test applying a method developed overseas using odors familiar to Japanese. Odor sticks are prepared by mixing microencapsulated odorous substances into Vaseline and molding into a lipstick-shape, and there are 12 types of smells (India ink, wood, perfume, menthol, mandarin orange, curry, gas for family use, roses, Japanese cypress, musty/sweaty socks, condensed milk, and fried garlic). An odor stick was smeared on a paper for wrapping medicine and folded in two, the smeared region was rubbed to generate smell, and the subject smelled it. For the answer, the subject selected the closest smell from the choices presented on the selection card (6 choices comprising 4 smells, ‘I don't know', and ‘odorless'). This test was performed using the 12 smell types. One correct answer was scored as 1, for 12 points in total. A score of 8 or lower was judged as lower olfactory function and 2 or lower was judged as anosmia. Subjects were not restricted from performing daily activities. The test was performed in the examiner-to-subject style in a room with air-conditioning and the score was regarded as the representative value of the olfactory function in the subject.
Cognitive function
Olfactory function decreases in dementia (12), which is included as a main cause of a condition requiring nursing (13). As the subjects of this survey were elderly persons requiring nursing care, the severity of dementia may have varied. Thus, cognitive function was evaluated using the HDS-R as a factor associated with olfactory function. The HDS-R is composed of 9 questions, being fewer that the number in other cognitive function tests. It takes approximately 10–15 minutes and no special conditions are necessary (14). In addition, it is unlikely to be influenced by age or years of schooling. The full score is 30 and dementia is highly suspected when the score is 20 or lower.
Appetite
Appetite was evaluated by an interview using the Council of Nutrition Appetite Questionnaire (CNAQ). The CNAQ is a questionnaire survey method widely used in Japan and other countries (15). There are 8 questions (Appendix) with 5 choices. The subjects selected an applicable choice and appetite was evaluated as follows: 8–16, there is a risk of anorexia; 17–28, frequent re-evaluation is necessary; 29 or higher, no risk at this point. The total score was regarded as the representative value of each subject.
Nutritional status
The serum albumin level is the representative index to evaluate the nutritional status, but it is inappropriate for the elderly because it is strongly influenced by diseases (16). In addition, blood sampling is invasive and increases the burden on the subjects. Thus, it was considered inappropriate for this survey. Of evaluation methods using body weight measurable at home, the body mass index (BMI), which can be easily and objectively calculated from the body weight and height, was used to evaluate the nutritional status (17). The BMI is a nutrition index frequently used to assess the nutritional status. The body weight and height of the elderly subjects requiring nursing care were acquired from their nursing records. For those not requiring nursing care, the body weight and height were measured, and the BMI was calculated on the survey day.
Analytical methods
As a significant difference was noted in the age between the elderly subjects requiring and not nursing care (p<0.05), the OSIT-J was compared using covariance analysis considering the age (95% confidence interval). In addition, factors that may be associated with olfactory function were similarly compared by covariance analysis (95% confidence interval).
Experiment II
Subjects
The subjects were the same 158 elderly persons requiring nursing care surveyed in Experiment I.
Survey items
The survey items were the same as those in Experiment I: the OSIT-J, HDS-R, CNAQ, and BMI. In addition, food intake was surveyed. Food intake was documented three times daily in their nursing notes. Staple food and dishes other than the staple food ingested in the last 3-month period were investigated, and the mean rate (%) of the total ingested food was calculated.
Analytical methods
To identify factors associated with olfactory function in the elderly requiring nursing care, a univariate linear regression analysis was performed with OSIT-J as the response variable, and the age, HDS-R, CNAQ, BMI, and food intake as the explanatory variables.
Results
Experiment I
Covariance analysis of the OSIT-J, HDS-R, CNAQ, and BMI as factors that may be associated with olfactory function was performed considering the age of the elderly subjects requiring and not requiring nursing care (Table 1). Values were expressed as the mean ± standard deviation; range. The OSIT-J scores of olfactory function were 3.5±2.7; 0–10 and 6.6±3.3; 0–12 for the elderly subjects requiring and not nursing care, respectively, demonstrating significantly lower olfactory function in the elderly subjects requiring nursing care (p<0.01). The mean score was 8 or lower in both groups, confirming the lower olfactory function in both groups. Regarding factors that may be associated with olfactory function, the scores of the HDS-R, CNAQ, and BMI were 19.5±4.7; 11–29, 28.4±3.5; 17–36, and 21.6±3.1; 13.3–30.6 kg/m2, respectively, for the elderly subjects requiring nursing care, and 25.6±4.4; 13–30, 29.4±3.3; 21–36, and 21.9±2.7; 18.0–29.3 kg/m2, respectively, for those not requiring nursing care. No significant difference was noted in the CNAQ or BMI, whereas a significant difference was noted in the HDS-R (p<0.01), confirming the significantly lower cognitive function in the elderly subjects requiring nursing care.
Table 1.
Means after covariance analysis of the elderly subjects requiring and not requiring nursing care
| Elderly subjects requiring nursing care (n=158) | Elderly subjects not requiring nursing care (n=37) | p-value | |
|---|---|---|---|
| OSIT-J (score) | 3.5±2.7; 0–10 | 6.6±3.3; 0–12 | < 0.01 |
| Age (years old) | - | - | - |
| HDS-R (score) | 19.5±4.7; 11–29 | 25.6±4.4; 13–30 | < 0.01 |
| CNAQ (score) | 28.4±3.5; 17–36 | 29.4±3.3; 21–36 | 0.43 |
| BMI (kg/m2) | 21.6±3.1; 13.3–30.6 | 21.9±2.7; 18.0–29.3 | 0.86 |
Values are expressed as the mean ± standard deviation; range. On covariance analysis considering the age, a significant difference was noted in the OSIT-J and HDS-R (p<0.01), confirming that olfactory and cognitive functions in the elderly subjects requiring nursing care were significantly poorer than those in the elderly subjects not requiring nursing care.
Experiment II
Food intake was reported for 90.8% of elderly subjects requiring nursing care.
Using the data, a univariate linear regression analysis was performed to identify factors associated with olfactory function in the elderly subjects requiring nursing care. The analysis demonstrated that age and the HDS-R were associated with olfactory function. Specifically, age was negatively correlated with olfactory function, whereas the HDS-R was positively correlated with olfactory function (Table 2). Olfactory function was not associated with the CNAQ, BMI, or food intake.
Table 2.
Univariate linear regression analysis of variables for the elderly requiring nursing care
| Variable | Regression coefficient | Standard error | Standardized coefficient | p-value |
|---|---|---|---|---|
| Age | −0.132 | 0.029 | −0.342 | < 0.001 |
| HDS-R | 0.210 | 0.043 | 0.362 | < 0.001 |
| CNAQ | −0.049 | 0.062 | −0.063 | 0.434 |
| BMI | −0.042 | 0.070 | −0.048 | 0.547 |
| Food intake | −0.024 | 0.015 | −0.123 | 0.125 |
Univariate linear regression analysis with OSIT-J as the response variable, and age, HDS-R, CNAQ, BMI, and food intake as the explanatory variables. An association with olfactory function was noted for age and cognitive function.
Discussion
Validity of the OSIT-J used in the survey of olfactory function
The identification capacity test is capable of evaluating olfactory function of the olfactory bulb over the olfactory center in the neurology field, and Sniffin’ Sticks® (Burghart Medizintechnik, GmbH, Wedel, Germany), UPSIT™ (Sensonics International, Pennsylvania, America), T&T olfactometer (Daiichi Yakuhin Sangyo Co., Ltd., Tokyo, Japan), and OSIT-J are available. Sniffin’ Sticks® is a simple test in which felt saturated with 12 types of smells is smelled, but many smells not familiar to Japanese are included such as cloves, anise, and licorice (18). As smells are recalled in connection with memories of the past, the test may not be accurate with unfamiliar smells. UPSIT™ also contains many unfamiliar smells (19) and 40 types of odors are to be smelled, taking time. The T&T olfactometer was developed in Japan and is used as the standard olfactory acuity test mainly in the otorhinolaryngology field. It is used to judge the grade of olfactory disturbance and therapeutic effects, but its use has not spread because odor contamination occurs and a large testing device is necessary (20). Compared with these, the OSIT-J is composed of smells familiar to Japanese, the number of smell types is 12, being fewer, and the device is easy to carry (10). Although the OSIT-J cannot be used for medical examination aiming at making a diagnosis because it has not been approved, its usefulness is high because its results are correlated with those of the T&T olfactometer (21). Thus, the OSIT-J is used not only for examining olfactory disturbance in the otorhinolaryngology field (22), but also for screening of neurodegenerative diseases causing olfactory disturbance as a prodrome (23).
Based the above, we selected the identification capacity test as an olfactory function test and used the OSIT-J developed for Japanese as a simple test method.
Olfactory function in the elderly requiring nursing care
When olfactory function was compared between the elderly subjects requiring and not requiring nursing care, it was significantly poorer in the subjects requiring nursing care. The representative diseases leading to a condition requiring nursing care in Japan include dementia and Parkinson disease (13), and it has been reported that olfactory function deteriorates due to these neurodegenerative diseases (12, 23, 24). It is possible that the elderly subjects requiring nursing care included those with these diseases. This study did not survey based on disease, but based on the elderly requiring nursing care with several chronic diseases. When the elderly requiring nursing care were handled as a group, the sense of smell was considered low. In addition, a significant difference was noted in the HDS-R after adjustment for age between the elderly subjects requiring and not requiring nursing care, suggesting background involvement of cognitive function in olfactory function.
The mean OSIT-J score was 8 or lower in both groups, demonstrating reduction of olfactory function in both groups. Olfactory function starts to decline in the 50s and it rapidly deteriorates after 70 years of age (4). The mean age of the elderly subjects requiring and not requiring nursing care was 84.4±7.1 and 81.2±5.9 years old, respectively, suggesting that olfactory function had declined due to age in both groups.
Factors associated with olfactory function in the elderly requiring nursing care
Schiffman (25) and Stafford et al. (26) reported that the decline in olfactory function leads to loss of appetite and may be associated with malnutrition, and Boesveldt et al. (27) reported that olfactory function was associated with appetite and nutritional status, albeit weakly. In contrast, Schubert (28) and Toussaint et al. (29) reported that olfactory function and nutritional status were not associated. To clarify whether aging and cognitive decline are associated with the lower olfactory function in the elderly requiring nursing care, and whether this decline is associated with appetite and BMI, factors associated with olfactory function were investigated in the elderly subjects requiring nursing care in Experiment II.
Consistent with previous studies (4, 12), our univariate linear regression analysis revealed that age and cognitive decline were associated with the lower olfactory function in the elderly subjects requiring nursing care. However, olfactory function was not associated with appetite, nutritional status, or food intake. Studies reported by Ansari (24), Schiffman (25), and Stafford et al. (26) suggested an association of olfactory function with appetite and nutritional status, but this may have been because the subjects were younger than those in our study, leading to different results. On the other hand, the results of studies involving the elderly reported by Schubert (28) and Toussaint et al. (29) were similar to those of this study. Lower olfactory function may not affect appetite or nutritional status in the elderly, and the following two intrinsic factors in the elderly are considered as reasons: 1. Physiological appetite: There are two types of appetite, appetite involving chemical stimulation from the sensory organs and physiological appetite for maintenance of life (1, 30, 31). In the elderly, appetite may become not readily induced by chemical stimulation, but they eat meals through physiological appetite. 2. Gustatory function: Olfactory function was surveyed in this study, but taste also chemically stimulates appetite in addition to smell. Although gustatory sensory intensity decreases with age, the olfactory sensory intensity is considered more likely to markedly decrease compared with the gustatory sensory intensity (32). As the senses of smell and taste are mixed and interact through associated areas (33, 34, 35), it is possible that chemical stimulation by the sense of taste complements the reduced sense of smell and maintains appetite. To clarify the association between the senses of smell and taste in the elderly, survey and investigation of gustatory function is necessary in the future.
The elderly subjects requiring nursing care in this study were staying in facilities and their living environment was different from that of the subjects not requiring nursing care. The following two environmental factors were considered to influence appetite and nutritional status of the elderly requiring nursing care, in addition to the physiological appetite and gustatory function described above: 1. Habit: Humans exhibit anticipatory eating (36). This is the phenomenon of a person eating meals at a regular time every day eating a specific amount at the regular meal time regardless of feeling hungry. Many of the subjects were staying in facilities and were provided with 3 meals at a regular time daily. Regular snack times were set depending on the health condition of the subjects. The subjects with such habituation may have had anticipatory eating and they may have ingested a specific amount, thereby maintaining their nutritional status. 2. Society: Caregivers are present for the elderly requiring nursing care staying in facilities. At facilities, the body weight and food intake are closely measured, and managed through meal planning and assistance for eating by caregivers, which may have been reflected in the results.
Limitation
Olfactory and cognitive function tests, and questionnaire about appetite may not have been possible unless communication was possible, thus only the elderly requiring nursing care with dementia up to a moderate level were surveyed. Communication becomes difficult with age and disease progression due to marked impairment of cognitive function in the elderly requiring nursing care. Malnutrition is problematic in the elderly with severe dementia requiring nursing care, and the association of olfactory function with appetite and nutritional status is unclear, for which further investigation is required.
Conclusions
Olfactory function in the elderly requiring nursing care was poorer than that in the elderly not requiring nursing care, and aging and cognitive decline were suggested to be associated with lower olfactory function. In addition, lower olfactory function in the elderly requiring nursing care was not associated with appetite, nutritional status, or food intake.
Acknowledgments
This study was supported by a grant from JSPS KAKENHI (No. JP18K09876, Grant-in-Aid for Scientific Research C).
Conflict of interest
The authors declare that there are no conflicts of interest regarding the publication of this manuscript.
Ethical standards
This study was performed after approval by the ethics committees of the School & Graduate School of Dentistry, Osaka University, and Osaka University Dental Hospital (approval number: H29-E24-1).
Electronic Supplementary Information
Supplementary material is available for this article at https://doi.org/10.1007/s12603-020-1334-3 and is accessible for authorized users.
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References
- 1.Donini L, Saina C, Carlo C. Eating habits and appetite control in the elderly: The anorexia of aging. International Psychogeriatrics. 2003;15:73–87. doi: 10.1017/s1041610203008779. 10.1017/S1041610203008779 [DOI] [PubMed] [Google Scholar]
- 2.Tanvir A, Nadim H. Assessment and management of nutrition in older people and its importance to health. Clin Interv Aging. 2010;5:207–216. doi: 10.2147/cia.s9664. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Rolls E. Taste, Olfactory and Food-texture Processing in the Brain and the Control of Appetite. Obesity Prevention 2010; 41–56.
- 4.Ayabe S, Saito K, Naito N, Mise M, Gotow N, Ichikawa H, Deguchi Y, Kobayakawa Y. Odor identification in different age and gender groups assessed by the Odor Stick Identification Test (OSIT) Aroma Research. 2005;6:368–371. [Google Scholar]
- 5.Umeda Y, Ishii S, Kameyama M, Kondo K, Ochi A, Yamasoba T, Ogawa S, Akishita M. Heterogeneity of odorant identification impairment in patients with Alzheimer’s Disease. Scientific Reports. 2017;7:1–7. doi: 10.1038/s41598-017-05201-7. 10.1038/s41598-016-0028-x [DOI] [PMC free article] [PubMed] [Google Scholar]
- 6.Roessner V, Bleich S, Banaschewski T, Rothenberger A. Olfactory deficits in anorexia nervosa. European Archives of Psychiatry and Clinical Neuroscience. 2005;255:6–9. doi: 10.1007/s00406-004-0525-y. 10.1007/s00406-004-0525-y [DOI] [PubMed] [Google Scholar]
- 7.Schreder T, Albrecht J, Kleemann A, Schöpf V, Kopietz R, Anzinger A, Demmel M, Linn J, Pollatos O, Wiesmann M. Olfactory performance of patients with anorexia nervosa and healthy subjects in hunger and satiety. Rhinology. 2008;46:175–183. PubMed PMID: 18853867. [PubMed] [Google Scholar]
- 8.Deems D, Doty R, Settle R, Mooregillon V, Shaman P, Mester A, Kimmelman C, Brightman V, Snow J. Smell and taste disorders, a study of 750 patients from the University of Pennsylvania Smell and Taste Center. Arch Otolaryngol Head Neck Surg. 1991;117(5):519–528. doi: 10.1001/archotol.1991.01870170065015. 10.1001/archotol.1991.01870170065015 [DOI] [PubMed] [Google Scholar]
- 9.Brod M, Stewart A L, Sands L. Conceptualization and Measurement of Quality of Life in Dementia: The Dementia Quality of Life Instrument (DQoL) The Gerontologist. 1999;39:25–36. doi: 10.1093/geront/39.1.25. 10.1093/geront/39.1.25 [DOI] [PubMed] [Google Scholar]
- 10.Doty R. The olfactory system and Its disorders. Seminars in Neurology. 2009;29:74–81. doi: 10.1055/s-0028-1124025. 10.1055/s-0028-1124025 [DOI] [PubMed] [Google Scholar]
- 11.Saito S, Ayabe S, Takashima Y, Gotow N, Naito N, Nozawa T, Mise M, Deguchi Y, Kobayakawa T. Development of a smell identification test using a novel stick-type odor presentation kit. Chemical Senses. 2006;31:379–391. doi: 10.1093/chemse/bjj042. 10.1093/chemse/bjj042 [DOI] [PubMed] [Google Scholar]
- 12.Mesholam R, Moberg P, Mahr R, Doty R. Olfaction in Neurodegenerative Disease. Arch Neurol. 1998;55:84–90. doi: 10.1001/archneur.55.1.84. 10.1001/archneur.55.1.84 [DOI] [PubMed] [Google Scholar]
- 13.Takahashi K, Tsukishima S. Diseases requiring severe-level care certification for long-term care insurance. The Japanese Journal of Public Health. 2017;64:655–663. doi: 10.11236/jph.64.11_655. PubMed PMID: 29249776. [DOI] [PubMed] [Google Scholar]
- 14.Imai Y, Hasegawa K. The revised Hasegawa’s dementia scale (HDS-R) - Evaluation of its usefulness as a screening test for dementia. Journal of the Hong Kong College of Psychiartrists. 1994;4:20–24. [Google Scholar]
- 15.Tokudome Y, Okumura K, Kumagai Y, Hirano H, Kim H, Morishita S, Watanabe Y. Development of the Japanese version of the Council on Nutrition Appetite Questionnaire and its simplified versions, and evaluation of their reliability, validity, and reproducibility. Journal of Epidemiology. 2017;27:524–530. doi: 10.1016/j.je.2016.11.002. 10.1016/j.je.2016.11.002 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 16.Kuzuya M, Izawa S, Enoki H, Okada K, Iguchi A. Is serum albumin a good marker for malnutrition in the physically impaired elderly? Clinical Nutrition. 2007;26:84–90. doi: 10.1016/j.clnu.2006.07.009. 10.1016/j.clnu.2006.07.009 [DOI] [PubMed] [Google Scholar]
- 17.Matthias P, Herbert L. Nutrition in the elderly. Best Practice & Research Clinical Gastroenterology. 2001;15:869–884. doi: 10.1053/bega.2001.0246. 10.1053/bega.2001.0246 [DOI] [PubMed] [Google Scholar]
- 18.Kobal G, Hummel T, Sekinger B. “Sniffin sticks screening of olfactory performance. Rhinology. 1996;34:222–226. PubMed PMID: 9050101. [PubMed] [Google Scholar]
- 19.Doty R, Shaman P, Kimmelman C, Dann S. University of Pennsylvania smell identification test: A rapid quantitative olfactory function test for the clinic. Laryngoscope. 1984;94:176–178. doi: 10.1288/00005537-198402000-00004. 10.1288/00005537-198402000-00004 [DOI] [PubMed] [Google Scholar]
- 20.Saiki K, Fukazawa O, Asaka H. T&T Olfactometer for Standardized Olfactory Test and Its Uses. Olfaction and Taste XI 2013;12–16.
- 21.Kobayashi M. The Odor Stick Identification Test for the Japanese (OSIT-J): Clinical Suitability for Patients Suffering from Olfactory Disturbance. Chemical Senses. 2005;30(suppl_1):i216–i217. doi: 10.1093/chemse/bjh191. 10.1093/chemse/bjh191 [DOI] [PubMed] [Google Scholar]
- 22.Shiga H, Toda H, Kobayakawa T, Saito S, Hirota K, Tsukatani T, Furukawa M, Miwa T. Usefulness of curry odorant of odor stick identification test for Japanese in olfactory impairment screening. Acta Otolaryngol Suppl. 2009;562:91–94. doi: 10.1080/00016480902915699. 10.1080/00016480902915699 [DOI] [PubMed] [Google Scholar]
- 23.Baba T, Kikuchi A, Hirayama K, Nishio Y, Hosokai Y, Kanno S, Hasegawa T, Sugeno N, Konno M, Suzuki K, Takahashi S, Fukuda H, Aoki M, Itoyama Y, Mori E, Takeda A. Severe olfactory dysfunction is a prodromal symptom of dementia associated with Parkinson’s disease: a 3 year longitudinal study. Brain. Pt 1 2012;135:161–169. doi: 10.1093/brain/awr321. 10.1093/brain/awr321 [DOI] [PubMed] [Google Scholar]
- 24.Ansari K, Johnson A. Olfactory function in patients with Parkinson’s disease. Journal of Chronic Diseases. 1975;28:493–497. doi: 10.1016/0021-9681(75)90058-2. 10.1016/0021-9681(75)90058-2 [DOI] [PubMed] [Google Scholar]
- 25.Schiffman S. The Use and Utility of Glutamates as Flavoring Agents in Foods Intensification of Sensory Properties of Foods for the Elderly. The Journal of Nutrition. 2000;130:927S–930S. doi: 10.1093/jn/130.4.927S. 10.1093/jn/130.4.927S [DOI] [PubMed] [Google Scholar]
- 26.Stafford L, Welbeck K. High hunger state increases olfactory sensitivity to neutral but not food odors. Chemical Senses. 2011;36:189–198. doi: 10.1093/chemse/bjq114. 10.1093/chemse/bjq114 [DOI] [PubMed] [Google Scholar]
- 27.Boesveldt S, Lindau S, McClintock M, Hummel T, Lundström J. Gustatory and olfactory dysfunction in older adults: A national probability study. Rhinology. 2011;49:324–330. doi: 10.4193/rhino10.155. PubMed PMID: 21858264, PMCID 3775551. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 28.Schubert C, Fischer M, Pinto A, Klein K, Klein R, Cruickshanks J. Odor detection thresholds in a population of older adults. The Laryngoscope. 2016;127:1258–1262. doi: 10.1002/lary.26457. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 29.Toussaint N, Roon M, Campen J, Kremer S, Boesveldt S. Loss of olfactory function and nutritional status in vital older adults and geriatric patients. Chemical Senses. 2015;40:197–203. doi: 10.1093/chemse/bju113. 10.1093/chemse/bju113 [DOI] [PubMed] [Google Scholar]
- 30.D A BOOTH M The Physiology of the Appetite. British Medical Bulletin. 1981;37:135–140. doi: 10.1093/oxfordjournals.bmb.a071690. 10.1093/oxfordjournals.bmb.a071690 [DOI] [PubMed] [Google Scholar]
- 31.Gregersen N, Møller B, Raben A. Determinants of appetite ratings: The role of age, gender, BMI, physical activity, smoking habits, and diet/weight concern. Food and Nutrition Research. 2011;55:1–10. doi: 10.3402/fnr.v55i0.7028. 10.3402/fnr.v55i0.7028 [DOI] [PMC free article] [PubMed] [Google Scholar]
- 32.Stevens J C, Cain W S. Age-related deficiency in the perceived. strength of six odorants. Chemical Senses. 1985;10(4):517–529. 10.1093/chemse/10.4.517 [Google Scholar]
- 33.Stevenson R, Tomiczek C. Olfactory-induced synesthesias: A review and model. Psychological Bulletin. 2007;133:294–309. doi: 10.1037/0033-2909.133.2.294. 10.1037/0033-2909.133.2.294 [DOI] [PubMed] [Google Scholar]
- 34.Sakai N, Kobayakawa T, Gotow N, Saito S, Imada S. Enhancement of sweetness ratings of aspartame by a vanilla odor presented either by orthonasal or retronasal routes. Percept Mot Skills. 2001;92:1002–1008. doi: 10.2466/pms.2001.92.3c.1002. 10.2466/PMS.92.3.1002-1008 [DOI] [PubMed] [Google Scholar]
- 35.Rapps N, Giel K, Söhngen E. Olfactory deficits in patients with anorexia nervosa. European Eating Disorders Review. 2010;18:285–389. doi: 10.1002/erv.1010. 10.1002/erv.1010 [DOI] [PubMed] [Google Scholar]
- 36.Pinel J P J, Assanand S, Lehman D R. Hunger, eating, and ill health. American Psychologist. 2000;55(10):1105–1116. doi: 10.1037//0003-066x.55.10.1105. 10.1037/0003-066X.55.10.1105 [DOI] [PubMed] [Google Scholar]
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