Importance: Cannabis use is associated with short-term memory impairment and long-term changes in brain structure; however, little is known about whether disordered cannabis use is associated with an increased risk of a dementia diagnosis.

Objective: To investigate the association between emergency department visits or hospitalizations (acute care encounters) due to cannabis and future dementia diagnosis.

Design, setting, and participants: Population-based, retrospective, matched cohort study using health administrative data from Ontario, Canada, between 2008 and 2021 (with follow-up until 2022) including all individuals aged 45 to 105 years living in Ontario who were eligible and did not have a diagnosis of dementia at cohort entry (2 620 083 individuals excluded).

Exposure: Individuals with incident acute care due to cannabis use, defined using International Classification of Diseases and Related Health Problems, Tenth Revision coding.

Main outcomes and measures: We used cause-specific adjusted hazard models to compare new diagnoses of dementia (from a validated algorithm) between individuals with acute care due to cannabis use with (1) individuals with all-cause acute care (excluding cannabis), (2) the general population, and (3) individuals with acute care due to alcohol use.

Results: The study included 6 086 794 individuals, of whom 16 275 (0.3%) had incident acute care due to cannabis use (mean age, 55.2 [SD, 8.3] years; 60.3% male). Annual rates of incident acute care due to cannabis use increased 5.0-fold in individuals aged 45 to 64 years (from 10.16 to 50.65 per 100 000) and 26.7-fold in individuals aged 65 years or older (from 0.65 to 16.99 per 100 000) between 2008 and 2021. Individuals with incident acute care due to cannabis use were at a 1.5-fold and 3.9-fold increased risk of dementia diagnosis within 5 years relative to individuals with all-cause acute care and the general population of the same age and sex, respectively (absolute rates of dementia diagnosis: 5.0% for cannabis-related acute care, 3.6% for all-cause acute care, and 1.3% in the general population). After adjustment for sociodemographics and chronic health conditions, individuals with acute care due to cannabis use remained at elevated risk relative to those with all-cause acute care (adjusted hazard ratio [aHR], 1.23; 95% CI, 1.09-1.39) and the general population (aHR, 1.72; 95% CI, 1.38-2.15). Individuals with acute care due to cannabis use were at lower risk than those with acute care due to alcohol use (aHR, 0.69; 95% CI, 0.62-0.76).

Conclusions and relevance: Individuals with cannabis use severe enough to require hospital-based care were at increased risk of a new dementia diagnosis compared with those with all-cause hospital-based care or the general population. These findings have important implications considering increasing cannabis use among older adults.

重要性： 大麻使用与短期记忆障碍和长期大脑结构变化有关；然而，对于紊乱的大麻使用是否增加了痴呆诊断的风险知之甚少。

目的： 研究由于大麻导致的急诊科就诊或住院（急性护理）与未来痴呆诊断之间的关联。

设计、设置和参与者： 一项基于人口的回顾性匹配队列研究，使用了2008年至2021年加拿大安大略省的健康行政数据（随访至2022年），包括所有年龄在45至105岁且未被诊断为痴呆症的安大略居民（排除了2,620,083名不符合条件的人）。

暴露： 因使用大麻而导致的急性护理事件，使用国际疾病分类第十版编码定义。

主要结果和测量指标： 我们使用特定原因调整后的风险模型，比较了由于大麻使用而进行急性护理的人与（1）所有原因引起的急性护理（不包括大麻），（2）一般人群以及（3）因酒精使用导致的急性护理人员新诊断痴呆症的发生率。

结果： 研究共纳入了6,086,794名个体，其中16,275人（0.3%）因大麻使用而首次接受急性护理（平均年龄为55.2岁 [标准差，8.3]；男性占60.3%）。在2008年至2021年间，45至64岁的个体因大麻使用导致的年度急性护理事件增加了5.0倍（从每十万人口中的10.16例增加到50.65例），而年龄为65岁或以上的个体该比例增加了26.7倍（从每十万人口中的0.65例增加到16.99例）。与所有原因的急性护理人员及相同年龄段和性别的普通人群相比，因大麻使用而导致的急性护理事件的人在未来五年内患痴呆的风险分别高出1.5倍和3.9倍（绝对诊断率：大麻相关急性护理为5.0%，所有原因急性护理为3.6%，一般人口为1.3%）。在调整社会人口学因素及慢性疾病后，因大麻使用而导致的急性护理事件的人仍比所有原因导致的急性护理人员高出风险（校正危害比[aHR]，1.23；95% CI, 1.09-1.39），以及一般人群（aHR，1.72；95% CI, 1.38-2.15）。因大麻使用而导致急性护理的个体患痴呆症的风险低于酒精使用导致急性护理的个体（aHR，0.69；95% CI, 0.62-0.76）。

结论和意义： 与所有原因引起的医院护理或一般人群相比，因大麻使用严重到需要住院治疗的个体出现新的痴呆诊断风险增加。这些发现对于考虑老年人中不断增加的大麻使用具有重要意义。