Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Department of Radiology, Mayo Clinic, Rochester, MN, USA.
J Alzheimers Dis. 2022;89(1):233-245. doi: 10.3233/JAD-220228.
Olfactory identification (OI) impairment appears early in the course of Alzheimer's disease dementia (AD), prior to detectable cognitive impairment. However, the neuroanatomical correlates of impaired OI in cognitively normal older adults (CN) and persons with mild cognitive impairment (MCI) are not fully understood.
We examined the neuroanatomic correlates of OI impairment in older adults from the Atherosclerosis Risk in Communities Neurocognitive Study (ARIC-NCS).
Our sample included 1,600 older adults without dementia who completed clinical assessment and structural brain imaging from 2011 to 2013. We characterized OI impairment using the 12-item Sniffin' Sticks odor identification test (score ≤6). We used voxel-based morphometry (VBM) and region of interest (ROI) analyses to examine the neuroanatomic correlates of impaired OI in CN and MCI, after adjusting for potential confounders. Analyses were also separately stratified by race and sex.
In CN, OI impairment was associated with smaller amygdala gray matter (GM) volume (p < 0.05). In MCI, OI impairment was associated with smaller GM volumes of the olfactory cortex, amygdala, entorhinal cortex, hippocampus, and insula (ps < 0.05). Differential associations were observed by sex in MCI; OI impairment was associated with lower insular GM volumes among men but not among women (p-interaction = 0.04). There were no meaningful interactions by race.
The brain regions associated with OI impairment in individuals without dementia are specifically those regions known to be the primary targets of AD pathogenic processes. These findings highlight the potential utility of olfactory assessment in the identification and stratification of older adults at risk for AD.
嗅觉识别（OI）障碍在阿尔茨海默病痴呆（AD）的早期阶段出现，早于可检测的认知障碍。然而，在认知正常的老年人（CN）和轻度认知障碍（MCI）人群中，OI 受损的神经解剖学相关性尚不完全清楚。
我们在 Atherosclerosis Risk in Communities Neurocognitive Study（ARIC-NCS）中研究了来自老年人群的 OI 损伤的神经解剖学相关性。
我们的样本包括 1600 名无痴呆症的老年人，他们在 2011 年至 2013 年期间完成了临床评估和结构脑成像。我们使用 12 项 Sniffin' Sticks 嗅觉识别测试（得分≤6）来描述 OI 损伤。我们使用基于体素的形态测量学（VBM）和感兴趣区（ROI）分析，在调整潜在混杂因素后，研究 CN 和 MCI 中 OI 受损的神经解剖学相关性。分析还分别按种族和性别进行分层。
在 CN 中，OI 损伤与杏仁核灰质（GM）体积较小相关（p＜0.05）。在 MCI 中，OI 损伤与嗅觉皮层、杏仁核、内嗅皮层、海马和岛叶 GM 体积较小相关（p＜0.05）。在 MCI 中按性别观察到不同的相关性；OI 损伤与男性的岛叶 GM 体积较低相关，但与女性无关（p 交互=0.04）。按种族无显著交互作用。
在无痴呆症的个体中，与 OI 损伤相关的大脑区域是已知 AD 致病过程的主要靶点的特定区域。这些发现突出了嗅觉评估在识别和分层 AD 风险老年人方面的潜在效用。
