Serum C-Reactive Protein Is Negatively Associated With Olfactory Identification Ability in Older Adults

Abstract

Importance Olfactory deficits are common in aging and associated with several conditions linked to inflammation. A few studies suggest that increased concentration of pro-inflammatory biomarkers may be related to olfactory deficits, but these associations are understudied in population-based samples. Objective To investigate the association between serum concentrations of C-reactive protein (CRP) and olfactory identification level as well as rate of change in aging. Methods We included 1,721 participants (mean age 70.5 years; 61.9% female) with at least two olfactory assessments across the 12-year follow-up. Baseline level and change in odor identification were estimated with linear mixed models as a function of CRP levels, derived from blood plasma at baseline. Results Results indicated a negative dose–response association between CRP level and odor identification scores at baseline, after adjustment for demographic, cognitive, health, and lifestyle factors. CRP levels ranging between 11 and 20 mg/L were significantly related to lower olfactory ability (β = −0.811, 95% confidence interval [CI] [−1.503 to −0.118]; p = .022). Likewise, CRP values above 20 mg/L were related to lower olfactory scores, an association that approached statistical significance (β = −0.996, 95% CI [−2.045 to 0.054]; p = .063). We found no associations between CRP and olfactory change ( ps > .368). Sensitivity analyses showed that associations between CRP and olfaction were confined to younger participants (age ≤72 years) and men ( ps < .034). Conclusions Our findings suggest a negative association between serum CRP levels and olfactory identification ability in aging that may be dependent on age and sex.

Factors Associated with Poor Olfaction and Olfactory Decline in Older Adults in the ARIC Neurocognitive Study

“…Based on the prior literature, we considered sociodemographic (age, sex, race, study site, and education), behavioral (smoking, alcohol consumption, and physical activity), vascular and/or metabolic (body mass index (BMI), serum total cholesterol, diabetes, hypertension status, coronary heart disease, and myocardial infarction), genetic (apolipoprotein E gene epsilon 4 allele ( APOE ε 4)), inflammatory (C-reactive protein), blood hemoglobin, and nutritional factor (serum vitamin B 12 ) as the potential risk factors of olfaction [ 17 , 18 , 19 , 20 , 21 , 22 ]. With the exception of sex, race, study site, and education, which were obtained from the visit 1 exam, other risk factors data were obtained from the visit 5 exam.…”

“…In older adults, the prevalence of olfactory impairment increases with age and is about two times as high in men as in women and similarly elevated in Black and White individuals [ 2 , 11 , 13 , 14 ]. Studies have also linked smoking [ 2 , 15 ], cardiovascular factors [ 16 , 17 ], diabetes [ 17 ], lower physical activity [ 18 ], and systemic inflammatory markers [ 19 ] with poor olfaction, but findings have been sparse and inconsistent [ 13 , 20 , 21 , 22 , 23 ]. Furthermore, the existing evidence on determinants of olfactory impairment mostly comes from cross-sectional studies [ 13 , 23 , 24 , 25 , 26 ], and only a few prospective studies have investigated the factors associated with longitudinal changes in olfactory function [ 17 , 21 , 22 ].…”

Effect of different odors on the rat urine proteome

“…Among the differential proteins identified, several proteins have been reported to be associated with olfaction.Ekström I et al [14] in 2021 showed that serum C-reactive protein (CRP) levels were negatively correlated with olfactory recognition in aging. And Proft F et al [15] found that diminished sense of smell in patients with granulomatous polyangiitis (GPA) was significantly associated with elevated CRP values.…”