Stroke Prevention Research Unit, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, UK.
Cerebrovasc Dis. 2013;36(5-6):355-62. doi: 10.1159/000355496. Epub 2013 Nov 8.
Mild cognitive impairment (MCI) is at least as prevalent as dementia after transient ischaemic attack (TIA)/stroke and is increasingly recognised as an important outcome in observational studies and randomised trials. However, there is no consensus on how impairment should be defined, and numerous different criteria exist. Previous studies have shown that different criteria for cognitive impairment impact on prevalence rates in epidemiological studies. However, there are few data on how operational differences within established criteria (e.g. Petersen-MCI) affect measured impairment rates and the performance of short cognitive tests such as the Mini Mental State Examination (MMSE) and the Montreal Cognitive Assessment (MoCA), particularly in cerebrovascular disease. We therefore evaluated the effect of different operational definitions on measured rates of Petersen-MCI and on reliability of short cognitive tests in patients with TIA and stroke.
Consecutive patients underwent the MMSE, MoCA and neuropsychological battery ≥1 year after TIA or stroke in a population-based study. MCI was defined using the Petersen method and subclassified as single or multiple domain, both with (original) and without (modified) subjective memory impairment. Different cut-offs (>1, >1.5 and >2 standard deviations, SD) on a given test relative to published norms were compared together with use of single versus multiple tests to define domain impairment.
91 non-demented subjects completed neuropsychological testing (mean age ± SD 69.7 ± 11.6 years, 54 male, 49 stroke) at a mean of 3.1 ± 1.9 years after the index event. Rates of cognitive impairment ranged from 14/91 (15%) for MCI-original at >2 SD cut-off to 61/91 (67%) MCI-modified at >1 SD cut-off, and the proportion of MCI that was multiple domain varied, e.g. 24/46 (52%) versus only 5/27 (20%) at 1 versus 2 SD cut-off for MCI-modified. Requirement for subjective memory complaint approximately halved estimates [e.g. 17 (19%) vs. 39 (43%) for MCI at 1.5 SD cut-off, single test definition], whereas use of multiple tests versus a single test to define a cognitive domain had less impact. In general, diagnostic accuracy was higher, and optimal cut-offs lower, on MMSE and MoCA for multiple-domain versus single-domain MCI, but the MoCA appeared superior for detecting MCI-modified, whereas the MMSE performed well in detecting MCI-original.
Even within established criteria for MCI, differences in operational methodology result in 4-fold variation in MCI estimates. Optimal MMSE and MoCA cut-offs are lower, and reliability more similar, when criteria for MCI are more stringent. Our findings have implications for sample size and adjusted relative risk calculations in randomised trials and for comparisons between studies.
轻度认知障碍（MCI）在短暂性脑缺血发作（TIA）/中风后至少与痴呆一样普遍，并且越来越被认为是观察性研究和随机试验中的重要结果。然而，如何定义损伤尚无共识，并且存在许多不同的标准。先前的研究表明，认知障碍的不同标准会影响流行病学研究中的患病率。但是，关于既定标准（例如，Petersen-MCI）内的操作差异如何影响测量的损伤率以及简短认知测试（例如 Mini 精神状态检查（MMSE）和蒙特利尔认知评估（MoCA）的表现，特别是在脑血管疾病中，数据很少。因此，我们评估了不同操作定义对 TIA 和中风后患者中 Petersen-MCI 测量率的影响，以及对简短认知测试的可靠性的影响。
在一项基于人群的研究中，连续患者在 TIA 或中风后至少 1 年接受了 MMSE，MoCA 和神经心理学测试。使用 Petersen 方法定义 MCI，并将其分为单域或多域，均伴有（原始）和不伴有（改良）主观记忆障碍。与发表的规范相比，在给定测试上使用大于 1、1.5 和 2 个标准差（SD）的不同截止值（>1、>1.5 和>2 SD），并比较使用单个测试与多个测试来定义域损伤。
91 名非痴呆患者在指数事件后平均 3.1 ± 1.9 年完成了神经心理学测试（平均年龄±标准差 69.7 ± 11.6 岁，54 名男性，49 名中风）。认知障碍的发生率范围从>2 SD 截止值的 14/91（15％）到>1 SD 截止值的 61/91（67％）MCI 改良，而多域 MCI 的比例也有所不同，例如，1/46（52％）与 5/27（20％）之间的差异在 1 与 2 SD 截止值之间用于 MCI 改良。主观记忆投诉的要求使估计值减半[例如，在 1.5 SD 截止值时，MCI 的 17（19％）与 39（43％）相比]，而使用多个测试与单个测试相比，定义认知域的影响较小。一般来说，对于多域与单域 MCI，MMSE 和 MoCA 的诊断准确性更高，最佳截止值更低，但是 MoCA 更适合检测 MCI 改良，而 MMSE 则适合检测 MCI 原始。
即使在 MCI 的既定标准内，操作方法的差异也会导致 MCI 估计值发生四倍的变化。当 MCI 的标准更严格时，MMSE 和 MoCA 的最佳截止值更低，可靠性更相似。我们的发现对随机试验中的样本量和调整后的相对风险计算以及对研究之间的比较都有影响。
