There is an emerging belief that electrically elicited blink reflexes (BR) may distinguish Alzheimer’s disease (AD) from other disorders characterized by memory dysfunction. To qualitatively and quantitatively distinguish the effects that electrical stimulation has over the blink reflex (eBR) recorded from patients with AD and healthy controls (HCs), we did a systematic review of the literature, and conducted a meta-analysis. Following our selected criteria, 94 AD patients and 97 HCs were identified from articles published in English between 1950 and 2017. Although the 3 responses (R1, R2 and R3) of the eBR were studied in a number of patients, only the R2 response was quantified in all studies. Thresholds and stimulation intensities parameters were found to be used in a miscellaneous form, and the majority of times, such parameters deviated from validated guidelines. The stimulation frequencies used to elicit the BR responses ranged between 0.14 and 0.2 Hz. These frequencies favored HCs compared with AD patients (odds ratio = 1.08; 95% CI = 0.30-1.85), I2 = 0% [P = .99]; Q = 271.89 [df = 7, P < .000]). Egger’s regression test suggested publication bias (intercept = 32.38; 95% CI = −8.98 to −3.2; P = .001). Our results unveiled key shortcomings in the data reported; such shortcomings need to be corrected in future AD research looking for obtaining more reliable and reproducible eBR studies; otherwise, interventions may be misleading.

中文翻译：

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阿尔茨海默病眼轮匝肌反射的三种伤害性反应：证据状态和荟萃分析

有一种新兴的观点认为电诱发的眨眼反射 (BR) 可以将阿尔茨海默病 (AD) 与其他以记忆功能障碍为特征的疾病区分开来。为了定性和定量区分电刺激对 AD 患者和健康对照 (HC) 记录的眨眼反射 (eBR) 的影响，我们对文献进行了系统回顾，并进行了荟萃分析。根据我们选择的标准，从 1950 年至 2017 年间发表的英文文章中确定了 94 名 AD 患者和 97 名 HC。尽管在许多患者中研究了 eBR 的 3 种反应（R1、R2 和 R3），但只有 R2 反应是在所有研究中量化。发现阈值和刺激强度参数以多种形式使用，并且大多数情况下，这些参数偏离了经验证的准则。用于引发 BR 响应的刺激频率介于 0.14 和 0.2 Hz 之间。与 AD 患者相比，这些频率有利于 HC（优势比 = 1.08；95% CI = 0.30-1.85），I2 = 0% [P = .99]；Q = 271.89 [df = 7，P < .000]）。Egger 回归测试表明存在发表偏倚（截距 = 32.38；95% CI = -8.98 至 -3.2；P = .001）。我们的结果揭示了报告数据中的主要缺陷；这些缺点需要在未来的 AD 研究中得到纠正，以寻求获得更可靠和可重复的 eBR 研究；否则，干预可能会产生误导。Q = 271.89 [df = 7，P < .000]）。Egger 回归测试表明存在发表偏倚（截距 = 32.38；95% CI = -8.98 至 -3.2；P = .001）。我们的结果揭示了报告数据中的主要缺陷；这些缺点需要在未来的 AD 研究中得到纠正，以寻求获得更可靠和可重复的 eBR 研究；否则，干预可能会产生误导。Q = 271.89 [df = 7，P < .000]）。Egger 回归测试表明存在发表偏倚（截距 = 32.38；95% CI = -8.98 至 -3.2；P = .001）。我们的结果揭示了报告数据中的主要缺陷；这些缺点需要在未来的 AD 研究中得到纠正，以寻求获得更可靠和可重复的 eBR 研究；否则，干预可能会产生误导。