[p4–343]: association between olfactory function and mild cognitive impairment: results of the heinz nixdorf recall study

While there is strong evidence for an association of olfactory dysfunction and Alzheimer's disease, studies investigating mild cognitive impairment (MCI) report diverging results (Vyhnalek et al., 2015; Djordjevic et al., 2008). Especially large population based studies examining age and sex differences are scarce (Wilson et al., 2007; Liang et al., 2016). The aim of our study was to examine the sex- and age-specific associations of olfactory function and MCI in a well characterized German population based study sample. We compared 230 men (68.5±7.2 years) and 273 women (68.2±7.2 years) with MCI diagnosed according to Petersen's criteria (Winblad et al., 2004) with 2118 cognitively normal participants (68.5±7.2, 49% men) from the third examination of the Heinz Nixdorf Recall Study (2010–2016). Participants underwent Sniffin’ Sticks Screening Test measuring olfactory function on a scale of 0–12 points, where higher scores indicate better performance. Further they performed a cognitive screening consisting of eight tests (eight wordlist immediate/delayed recall, labyrinthtest, naming animals, clock-drawing test, trail-making test A/B, stroop task). To examine the association of olfactory function (linear, rescaled for analysis) with MCI (yes/no), we performed logistic regression models stratified by age-group (young-age: ≤64 years; middle-age: 65–74 years; old-age: ≥75 years) and gender (odds ratio (OR), 95% confidence interval (CI)). All regression models were performed unadjusted as well as adjusted for age, education and smoking status. Descriptive analyses of olfactory function showed lower mean scores for men with MCI (8.68±2.0) compared to women with MCI (8.99±2.1). Similar trend is found in cognitively normal patients (men:8.99±1.9, women:9.43±1.8). The regression analysis showed an association between olfactory performance and MCI in middle aged women only (adjusted OR=1.20, CI 1.07–1.36). We found no associations for the young-age group (OR=0.99; CI 0.86–1.14) or old-age group (OR=1.06; CI 0.94–1.18) in women. There were no associations found in men (young-age: OR=1.06, CI 0.91–1.23; middle-age: OR=1.06, CI 0.94–1.19; old-age: OR=1.04, CI 0.92–1.18). In this study worse olfactory function appears to be associated with MCI in middle-aged women. This is the first study reporting on age and gender specific associations between olfactory function and MCI. Longitudinal studies are necessary to confirm these results.