Date of Award

Summer 8-9-2019

Level of Access

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Food Science and Human Nutrition

Advisor

Mary E. Camire

Second Committee Member

Mona Therrien

Third Committee Member

Valerie Duffy

Abstract

Olfactory impairment is a prevalent but underreported condition among older adults in the United States (U.S.). In the elderly, this impairment is associated with a host of adverse health conditions and issues that affect the quality of life. This study investigated the prevalence of smell disorders in older adults over 60 years of age, the potential risk factors for smell deterioration, and the influence of smell dysfunction on health status using the data collected through the National Health and Nutrition Examination Survey (NHANES) 2013-2014 questionnaires and examination components.

Participants were categorized as smell impaired (‘SI Present’) if they were unable to identify five or more of the scents correctly. Similarly, participants were classified as having a smell alteration (‘SA Present’) if they reported: a problem in smell in the past 12 months, worse sense of smell since age 25 and or a phantom smell. A total of 1287 people were suitable for inclusion. The NHANES participants included for these analyses were mainly non-Hispanic white (52.7%), college-educated (54.5%), and lived with someone (60%). Among subjects, 279 persons were smell-impaired, and 44.8% of those individuals were aged 75-80. The prevalence for the general U.S population of smell impairment was 15.4% and 17.5% for smell alteration. Meanwhile, the incidence of smell dysfunction (smell impairment and or smell alteration) in the U.S. population was 29.8%. After adjusting for confounding variables in logistic regression, smell impairment was significantly associated with age 75-80 years (OR: 3.51, CI: 2.07-5.95), and an educational level of high school or less (OR: 1.70, CI: 1.40-2.30), poor health self-ratings (OR: 2.63, CI: 1.30-5.40), more sedentary hours each day (OR: 1.07, CI: 1.03-1.11), and presence of smell alteration (OR: 3.00, CI: 2.10-4.60). Furthermore, persons with normal muscle and hand grip strength were less likely to have a smell impairment or alteration. However, the role of appetite could not be determined because responses of “poor appetite” were coded as yes and tallied with “overeating” responses. Factors significantly associated with lower risks for smell impairment were being female, younger (in the 60-64 age range), not IADL (Instrumental Activities of Daily Living) impaired, and physically active. Moreover, smoking, appetite, weight changes, and other self-reported smell variables were not significantly associated with the presence of a smell disorder.

Overall, based on our findings, the prevalence of smell dysfunction increases with age. However, this change does not happen until the age of 75. This dysfunction also has adverse effects on the health status of older adults in the U.S. Healthcare practitioners may be able to improve the quality of life of patients by screening for smell alterations and developing early interventions.

Further prospective studies are warranted to investigate the causal links between olfactory impairment, medication, smoking, cognitive function, and food intake. Further research is also needed to determine whether preservation of olfaction can forestall age-related reductions in appetite, and subsequent loss in body mass, particularly muscle. The inclusion of persons older than 80 years in the NHANES sampling would provide useful data for researchers since the number of persons older than eighty is growing in this nation and elsewhere.

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