To the Editor In 1968, Kline¹ noted that lithium was a “different key” for dealing with affective and possibly other psychiatric disorders and asked the rhetorical question, “How many locks will it fit?” Kessing and colleagues² linked lithium in drinking water with dementia incidence, suggesting another lock for the lithium key. Lithium’s multifaceted, potentially neuroprotective actions do give it plausibility as an “elixir.” However, the study is not without its limitations. The lithium intake was based on sampling of waterworks that provide water to 42% of the population, and the sampling was done for 4 years (2009-2013) and extrapolated to a lifetime. Many potential confounders were not taken into consideration. A major source of lithium is diet, and some bottled water contains lithium. Both these factors are not accounted for in this study. No effort was made to substantiate the differential exposure by obtaining blood or hair lithium levels. Dementia rates are confounded by education, socioeconomic, and multiple health factors, which were not considered in the analysis. Furthermore, the explanation for the observation that low levels of exposure increased the risk of dementia was not satisfactory, and the lack of specificity for a neurodegenerative disorder again raises doubts about the veracity of this finding.

致编辑1968年，Kline ¹指出锂是应对情感和其他精神疾病的“不同钥匙”，并提出了反问性问题：“它能装多少把锁？” 凯辛和同事²饮用水中的锂与痴呆症的发生有关，这暗示了锂钥匙的另一锁定。锂的多方面的，潜在的神经保护作用确实使它有可能成为“ el剂”。但是，这项研究并非没有局限性。锂的摄入量是根据对42％的人口提供水的自来水厂的采样而得出的，采样时间为4年（2009-2013年），并推断出寿命。没有考虑许多潜在的混杂因素。锂的主要来源是饮食，有些瓶装水含有锂。这两项因素均未在本研究中说明。没有通过获取血液或头发中锂的含量来证实差异暴露的努力。痴呆症的发生率受教育，社会经济因素和多种健康因素的干扰，分析中未考虑的内容。此外，对于低水平暴露会增加痴呆症风险的观察结果的解释并不令人满意，并且对神经退行性疾病缺乏特异性再次使人们对该结果的准确性产生怀疑。