Background:It is controversial whether B12 deficiency causes dementia or B12 treatment can prevent dementia. Objective:To assess associations between low plasma (P-)B12 levels, B12 treatment, and risk of Alzheimer’s disease (AD; primary outcome) and all-cause or vascular dementia (secondary outcomes). Methods:We conducted a population-based cohort study using Danish registry data to assess associations between low P-B12 levels, high-dose injection or oral B12 treatment, and risk of dementia (study period 2000–2013). The primary P-B12 cohort included patients with a first-time P-B12 measurement whose subsequent B12 treatment was recorded. The secondary B12 treatment cohort included patients with a first-time B12 prescription and P-B12 measurement within one year before this prescription. For both cohorts, patients with low P-B12 levels (<200 pmol/L) were propensity score-matched 1:1 with patients with normal levels (200–600 pmol/L). We used multivariable Cox regression to compute 0–15-year hazard ratios for dementia. Results:For low P-B12 and normal P-B12 level groups, we included 53,089 patients in the primary P-B12 cohort and 13,656 patients in the secondary B12 treatment cohort. In the P-B12 cohort, hazard ratios for AD centered around one, regardless of follow-up period or treatment during follow-up. In the B12 treatment cohort, risk of AD was unaffected by low pre-treatment P-B12 levels, follow-up period and type of B12 treatment. Findings were similar for all-cause and vascular dementia. Conclusion:We found no associatio1n between low P-B12 levels and dementia. Associations were unaffected by B12 treatment. Results do not support routine screening for B12 deficiency in patients with suspected dementia.

中文翻译：

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血浆维生素 B12 水平、大剂量维生素 B12 治疗和痴呆风险

背景：维生素 B12 缺乏会导致痴呆还是维生素 B12 治疗可以预防痴呆存在争议。目的：评估低血浆 (P-)B12 水平、B12 治疗与阿尔茨海默病（AD；主要结果）和全因或血管性痴呆（次要结果）风险之间的关联。方法：我们使用丹麦注册数据进行了一项基于人群的队列研究，以评估低 P-B12 水平、高剂量注射或口服 B12 治疗与痴呆症风险之间的关联（研究期 2000-2013）。主要 P-B12 队列包括首次进行 P-B12 测量的患者，其随后的 B12 治疗被记录下来。二级 B12 治疗队列包括首次服用 B12 处方且在该处方前一年内进行 P-B12 测量的患者。对于两个队列，低 P-B12 水平的患者 (< 200 pmol/L) 与正常水平 (200–600 pmol/L) 患者的倾向得分匹配 1:1。我们使用多变量 Cox 回归来计算痴呆症的 0-15 年风险比。结果：对于低 P-B12 和正常 P-B12 水平组，我们在主要 P-B12 队列中纳入了 53,089 名患者，在次要 B12 治疗队列中纳入了 13,656 名患者。在 P-B12 队列中，无论随访期或随访期间的治疗如何，AD 的风险比都以 1 为中心。在维生素 B12 治疗队列中，AD 风险不受治疗前低 P-B12 水平、随访期和维生素 B12 治疗类型的影响。全因痴呆和血管性痴呆的结果相似。结论：我们发现低 P-B12 水平与痴呆症之间没有关联。协会不受 B12 治疗的影响。