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Background: Olfactory dysfunction has been suggested to be associated with all-cause mortality. Yet, there is a lack of large-scale cohorts to study this relationship., Methods: Using data from the Kailuan cohort, we assessed 97 327 Chinese adults for perceived olfactory dysfunction at baseline and gathered mortality data from government records. We used Cox proportional hazards regression models to analyse the risk of all-cause mortality associated with perceived olfactory dysfunction, yielding hazard ratios (HRs) and 95% confidence intervals (CIs) with adjustment for multiple potential confounders., Results: Over a median follow-up of 6.4-year, we recorded a total of 3903 deaths. Individuals reporting perceived olfactory dysfunction had a higher risk of mortality (adjusted HR = 1.42; 95% CI = 1.02-2.00) compared to those without the dysfunction. In sensitivity analyses, we found similar results after excluding participants with pre-existing obesity, cardiovascular diseases, those younger than 50 years old, individuals diagnosed with cancer or stroke during follow-up, and those who died within two years of follow-up., Conclusions: Perceived olfactory dysfunction was associated with a high risk of all-cause mortality among Chinese adults. Our study is limited by failure to include a national-representative sample and misclassification of exposure assessment due to use of a subjective question to assess olfactory dysfunction. Further studies with objective are warranted to replicate our findings and understand the underlying mechanisms., Competing Interests: Disclosure of interest: The authors completed the ICMJE Disclosure of Interest Form (available upon request from the corresponding author) and disclose no relevant interests., (Copyright © 2024 by the Journal of Global Health. All rights reserved.)

The effects of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) exist on a spectrum. Clinical symptoms of smell and taste dysfunction are prominent features of COVID-19. The objective of this study was to elucidate the factors associated with smell and taste dysfunction amongst hospitalized COVID-19 patients. A retrospective review of a multi-hospital health network's COVID-19 database between March and June 2020 was performed. Patients with self-reported smell or taste loss were included. Demographic information, patient comorbidities, and mortality data was obtained. There were 2892 patients included in this analysis and 117 reported smell or taste loss (4.0%, 95% confidence interval [CI]: 3.4%-4.8%). The proportion of females with smell or taste loss was significantly higher than males (6.3% vs. 2.5%, P < 0.001), whereas no differences existed between ethnicity or smoking status. When compared with age of 30-40 years, the age group of 10-20 years were most likely to present with smell or taste dysfunction (odds ratio [OR] 6.59, 95% CI 1.32-26.12; P = 0.01). The majority of specific comorbidities were not associated with increased incidence of smell or taste dysfunction. Outpatient healthcare workers were more likely to present with smell or taste loss (OR 3.2, CI 1.8-5.47; P < 0.001). The mortality rate among COVID-19 patients with smell or taste dysfunction was significantly lower than those without (0% vs. 20.3%; P < 0.001). Smell or taste loss is more prevalent in women, younger age groups, and healthier individuals. It may be associated with lower mortality and a milder disease trajectory compared to the overall cohort., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Background: Poor olfaction is common among older adults and has been linked to higher mortality. However, most studies have had a relatively short follow-up and have not explored potential explanations., Objective: To assess poor olfaction in relation to mortality in older adults and to investigate potential explanations., Design: Community-based prospective cohort study., Setting: 2 U.S. communities., Participants: 2289 adults aged 71 to 82 years at baseline (37.7% black persons and 51.9% women)., Measurements: Brief Smell Identification Test in 1999 or 2000 (baseline) and all-cause and cause-specific mortality at 3, 5, 10, and 13 years after baseline., Results: During follow-up, 1211 participants died by year 13. Compared with participants with good olfaction, those with poor olfaction had a 46% higher cumulative risk for death at year 10 (risk ratio, 1.46 [95% CI, 1.27 to 1.67]) and a 30% higher risk at year 13 (risk ratio, 1.30 [CI, 1.18 to 1.42]). Similar associations were found in men and women and in white and black persons. However, the association was evident among participants who reported excellent to good health at baseline (for example, 10-year mortality risk ratio, 1.62 [CI, 1.37 to 1.90]) but not among those who reported fair to poor health (10-year mortality risk ratio, 1.06 [CI, 0.82 to 1.37]). In analyses of cause-specific mortality, poor olfaction was associated with higher mortality from neurodegenerative and cardiovascular diseases. Mediation analyses showed that neurodegenerative diseases explained 22% and weight loss explained 6% of the higher 10-year mortality among participants with poor olfaction., Limitation: No data were collected on change in olfaction and its relationship to mortality., Conclusion: Poor olfaction is associated with higher long-term mortality among older adults, particularly those with excellent to good health at baseline. Neurodegenerative diseases and weight loss explain only part of the increased mortality., Primary Funding Source: National Institutes of Health and Michigan State University.

Background: Olfactory dysfunction might unveil the association between ageing and frailty, as it is associated with declining cognitive function, depression, reduced physical performance, reduced dietary intake, and mortality; all these conditions are characterized by increased levels of inflammatory parameters. The present study is aimed at evaluating the association between olfactory dysfunction, frailty, and mortality and whether such association might be mediated by inflammation., Methods: We analysed data of 1035 participants aged 65+ enrolled in the "InCHIANTI" study. Olfactory function was tested by the recognition of the smells of coffee, mint, and air. Olfactory dysfunction was defined as lack of recognition of at least two smells. Considering the items "shrinking," "exhaustion," "sedentariness," "slowness," and "weakness" included in the Fried definition, frailty was defined as the presence of at least three criteria, prefrailty of one or two, and robustness of none. Serum interleukin-6 (IL-6) was measured in duplicate by high-sensitivity enzyme-linked immunosorbent assays. Logistic regression was adopted to assess the association of frailty with olfactory function, as well as with the increasing number of olfactory deficits. Cox regression was used to test the association between olfactory dysfunction and 9-year survival., Results: Olfactory dysfunction was associated with frailty, after adjusting (OR 1.94, 95% CI = 1.07-3.51; P = .028); analysis of the interaction term indicated that the association varied according to interleukin-6 levels ( P for interaction = .005). Increasing levels of olfactory dysfunction were associated with increasing probability of being frail. Also, olfactory dysfunction was associated with reduced survival (HR 1.52, 95% CI = 1.16-1.98; P = .002); this association varied according to the presence of frailty ( P for interaction = .017) and prefrailty status ( P for interaction = .046), as well as increased interleukin-6 levels ( P for interaction = .011)., Conclusions: Impairment of olfactory function might represent a marker of frailty, prefrailty, and consequently reduced survival in an advanced age. Inflammation might represent the possible link between these conditions.

Recent work suggests that olfactory dysfunction is a strong predictor of five-year mortality in older adults. Based on past work showing: 1) that olfactory dysfunction impairs social functioning and 2) that social ties are linked with mortality, the current work explored whether impairments in social life mediated the relationship between olfactory dysfunction and mortality. Additionally, based on work showing gender differences in the social consequences of olfactory dysfunction, gender was assessed as a potential moderator of this association. Social network size mediated the olfactory-mortality link for females. To probe what feature of social networks was driving this effect, we investigated two subcomponents of social life: emotional closeness (e.g., perceived social support, loneliness) and physical closeness (e.g., physical contact, in-person socializing with others). Physical closeness significantly mediated the olfactory-mortality link for females, even after controlling for social network size. Emotional closeness did not mediate this link. Possible mechanisms underlying this relationship are discussed.

Objective: To examine the association between odor identification deficits and future mortality in a multiethnic community cohort of older adults., Methods: Participants were evaluated with the 40-item University of Pennsylvania Smell Identification Test (UPSIT). Follow-up occurred at 2-year intervals with information on death obtained from informant interviews and the National Death Index., Results: During follow-up (mean = 4.1 years, standard deviation = 2.6), 349 of 1,169 (29.9%) participants died. Participants who died were more likely to be older (p < 0.001), be male (p < 0.001), have lower UPSIT scores (p < 0.001), and have a diagnosis of dementia (p < 0.001). In a Cox model, the association between lower UPSIT score and mortality (hazard ratio [HR] = 1.07 per point interval, 95% confidence interval [CI] = 1.05-1.08, p < 0.001) persisted after controlling for age, gender, education, ethnicity, language, modified Charlson medical comorbidity index, dementia, depression, alcohol abuse, head injury, smoking, body mass index, and vision and hearing impairment (HR = 1.05, 95% CI = 1.03-1.07, p < 0.001). Compared to the fourth quartile with the highest UPSIT scores, HRs for mortality for the first, second, and third quartiles of UPSIT scores were 3.81 (95% CI = 2.71-5.34), 1.75 (95% CI = 1.23-2.50), and 1.58 (95% CI = 1.09-2.30), respectively. Participant mortality rate was 45% in the lowest quartile of UPSIT scores (anosmia) and 18% in the highest quartile of UPSIT scores., Interpretation: Impaired odor identification, particularly in the anosmic range, is associated with increased mortality in older adults even after controlling for dementia and medical comorbidity., (© 2015 American Neurological Association.)

Prediction of mortality has focused on disease and frailty, although antecedent biomarkers may herald broad physiological decline. Olfaction, an ancestral chemical system, is a strong candidate biomarker because it is linked to diverse physiological processes. We sought to determine if olfactory dysfunction is a harbinger of 5-year mortality in the National Social Life, Health and Aging Project [NSHAP], a nationally representative sample of older U.S. adults. 3,005 community-dwelling adults aged 57-85 were studied in 2005-6 (Wave 1) and their mortality determined in 2010-11 (Wave 2). Olfactory dysfunction, determined objectively at Wave 1, was used to estimate the odds of 5-year, all cause mortality via logistic regression, controlling for demographics and health factors. Mortality for anosmic older adults was four times that of normosmic individuals while hyposmic individuals had intermediate mortality (p<0.001), a "dose-dependent" effect present across the age range. In a comprehensive model that included potential confounding factors, anosmic older adults had over three times the odds of death compared to normosmic individuals (OR, 3.37 [95%CI 2.04, 5.57]), higher than and independent of known leading causes of death, and did not result from the following mechanisms: nutrition, cognitive function, mental health, smoking and alcohol abuse or frailty. Olfactory function is thus one of the strongest predictors of 5-year mortality and may serve as a bellwether for slowed cellular regeneration or as a marker of cumulative toxic environmental exposures. This finding provides clues for pinpointing an underlying mechanism related to a fundamental component of the aging process.

Background: Population-based data on the relationship between impaired olfaction and risk of mortality among older adults are lacking. We used a representative cohort of adults aged 60 years or older to assess whether olfactory loss is a predictor of mortality, independent of potential confounders., Methods: Olfaction was measured by the San Diego Odor Identification Test (SDOIT) among 1,636 participants enrolled in the Blue Mountains Eye Study (2002-2004). Five-year all-cause mortality was confirmed using the Australian National Death Index., Results: More than one in five participants (21.8%) with olfactory impairment had died over the 5 years compared with less than 10% of participants without olfactory loss. Moderate olfactory loss (SDOIT score ≤3) was associated with a 68% increased risk of all-cause mortality (multivariable-adjusted hazard ratio, 1.68; 95% confidence interval, 1.10-2.56). This association did not persist after further adjustment for cognitive impairment. The association between olfactory loss and all-cause mortality was more marked among older participants (≥70 years) than younger participants (<70 years) with olfactory impairment (multivariable-adjusted hazard ratio, 1.48; 95% confidence interval, 1.02-2.15). However, adjusting for cognitive impairment diminished this association., Conclusions: Older adults with moderately impaired olfaction compared with those with normal olfaction had a higher risk of dying 5 years later. The relationship between olfaction and mortality, however, may be largely mediated by cognitive impairment in these older adults. Our findings highlight the value of identifying olfactory loss in the preclinical stage in the older patient before the development of related comorbidities.

The association of olfactory dysfunction with mortality was examined in 1162 older persons without dementia or Parkinson's disease. They completed a standard 12-item test of odor identification and then were followed for a mean of 4.2 years (standard deviation [SD] = 2.6, range: 0-9) during which 321 individuals died (27.6%). The relation of olfactory score to risk of death was assessed in a series of proportional hazards models adjusted for age, sex, education, and other covariates. Olfactory scores ranged from 0 to 12 correct (mean = 9.0, SD = 2.2). In an initial analysis, risk of death decreased by about 6% for each additional odor correctly identified (hazard ratio = 0.94; 95% confidence interval: 0.90, 0.98). Thus, mortality risk was about 36% higher with a low score (6, 10th percentile) compared with a high score (11, 90th percentile). The association persisted in subsequent analyses that controlled for naming ability, disability, cerebrovascular disease, characteristic patterns of leisure activity, depressive symptoms, and apolipoprotein E genotype. The results indicate that difficulty identifying familiar odors in old age is associated with increased risk of death.