Clinical Manifestations

Olfactory decline is correlated with cognitive decline in aging. The National Institutes of Health Toolbox Odor Identification Test (NIHTB-OIT) is an established measure of olfaction ability. While it distinguishes differences in English-speaking samples with varying cognitive abilities, its validation has not been completed for Spanish-speaking and LatinX populations, who are far more likely to develop Alzheimer's than non-Latinos. We evaluated the NIHTB-OIT results from a cross-sectional sample of Spanish-speaking older adults.

In the context of Advancing Reliable Measurement in Alzheimer's Disease and Cognitive Aging (ARMADA) Study, we evaluated 239 Spanish-speaking adults aged 53 to 89: 115 normal controls (NC) (70.2% female; M_age = 73.19, SD_age = 4.99), 104 patients with mild cognitive impairment (MCI) diagnosis (68% female; M_age = 76.56, SD_age = 6.23), and 20 patients with Dementia of Alzheimer Type (DAT) diagnosis (70% female; M_age = 76.95, SD_age = 7.76). The NIHTB-OIT was administered by trained examiners using scratch-and-sniff cards for odor identification. Participants' performance is evaluated based on correct responses, with total raw scores ranging between 0 and 9. We analyzed the data using ANOVA for main effects and interactions, and Welch Two Sample t-tests for sex differences.

Results indicated main effects of age (F(1, 230) = 13.27, p < .001, ηp2 = .055), diagnosis (F(1, 230) = 3.59, p = .029, ηp2 = .030), and sex (F(1, 230) = 6.21, p = .013, ηp2 = .026). Older adults had lower scores on the NIHTB-OIT. No pairwise comparison was significant across normal controls, MCI, and DAT groups. We observed sex differences only for the healthy agers (p < .001), with female participants (M = 6.24, SD = 1.56) having higher scores than males (M = 5.32, SD = 1.70). There was no significant interaction between age and diagnosis, while the interaction between age and cognitive status was significant. Finally, a three-way interaction was observed between age, sex, and cognitive status (see Figure 1).

Among Spanish-speaking older adults, clinical groups displayed different trajectories in their performance on the NIHTB-OIT by both cognitive status and gender, suggesting heterogeneous clinical manifestations in odor detection ability with increasing age.