Effect of Chronic Kidney Disease on Olfactory Function: A Case-Control Study

Background: Olfactory function of patients with chronic kidney disease (CKD) has been found to be defective, and patients are often unaware of it. This predisposes them to malnutrition with consequence on health recovery and quality of life. Aim: To assess the olfactory function and determine the pattern of olfactory dysfunction in patients with CKD attending the University College Hospital, Ibadan. Materials and Methods: This was a prospective, hospital-based case-control study of adult patients with CKD. The control group were age- and sex-matched individuals without CKD. Olfactory threshold (OT), odor discrimination (OD), and odor identification (OI) tests were carried out in participants using the "Sniffin Sticks." Results: There were 100 patients with CKD and 100 healthy controls, age ranges between 19 to 86 years (mean +/- SD = 46.3 +/- 13.9 years) and 20 to 85 years (mean +/- SD = 43.4 +/- 14.9 years), respectively. There was no statistically significant difference between cases and control gender distribution (P = .57). The mean olfactory scores were significantly lower among the cases than control, OI 11.2 +/- 2.3 and 13.1 +/- 1.2 (P < .001), OD 8.5 +/- 2.4 and 10.9 +/- 1.5 (P < .001), OT 6.4 +/- 2.5 and 9.6 +/- 1.9 (P < .001), and threshold discrimination and identification 26.0 +/- 5.7 and 33.6 +/- 3.3 (P < .001), respectively. Prevalent olfactory dysfunction among patients with CKD was 77% (hyposmia 72%, anosmia 5%), and the control was 16% (all hyposmia; P < .001). Conclusion: There was high prevalence of olfactory dysfunction among patients with CKD, and the affectation is more at the central olfactory pathway.