In a population-based cohort study of more than 6 million adults in Ontario, Canada, patients who received emergency department or hospital care for cannabis use had an elevated risk of developing dementia compared with those without cannabis-related acute care encounters.
Investigators included 16,275 adult patients aged 45 to 105 years with no prior dementia diagnosis who had a first-time hospital or emergency department visit for cannabis use between 2008 and 2021, with follow-up through 2022. Cannabis encounters were identified using ICD-10 codes F12.X and T40.7.
At 5 years, 5.0% of the patients were diagnosed with dementia compared with 3.6% of those with all-cause acute care and 1.3% of the general population matched by age and sex. At 10 years, the dementia rate among cannabis-related acute care patients rose to 18.6%.
After adjusting for demographics, chronic health conditions, and prior substance use and mental health care, the patients with cannabis-related acute care had a 23% higher risk of dementia compared with those with all-cause acute care (adjusted hazard ratio [HR] = 1.23, 95% confidence interval [CI] = 1.08–1.39) and a 72% higher risk compared with the general population (adjusted HR = 1.72, 95% CI = 1.38–2.15).
“By 10 years, 18.6% of [patients] with cannabis-related acute care were diagnosed with dementia,” said lead study author Daniel T. Myran, MD, MPH, of the Ottawa Hospital Research Institute, and his colleagues.
The incidence of cannabis-related acute care increased over time, particularly after 2015. Among adults aged 65 years and older, the rate rose from 0.65 to 16.99 per 100,000, a 26.7-fold increase. In adult patients aged 45 to 64 years, the rate increased fivefold, from 10.16 to 50.65 per 100,000.
Compared with the patients who received acute care for alcohol use, those treated for cannabis-related causes had a lower risk of developing dementia (adjusted HR = 0.69, 95% CI = 0.62–0.76).
Secondary analyses showed that patients with cannabis-related acute care were at higher risk of early-onset dementia (prior to age 65 years) and delirium compared with the general population. The adjusted HR for early-onset dementia was 2.04 (95% CI = 1.50–2.79), and for delirium, 2.26 (95% CI = 1.88–2.73). No association was observed between cannabis-related care and hearing loss, which was used as a negative control.
Sensitivity analyses excluding those with prior mental health or substance use visits, or with delirium present at the time of dementia diagnosis, yielded consistent results.
The investigators reported an E-value of 2.84 for the general population comparison, suggesting that a strong unmeasured confounder would be needed to fully explain the observed association.
The study was not designed to assess causality. The investigators acknowledged limitations, including a lack of data on cannabis frequency, dose, and method of use. They declared no conflicts of interest.
Source: JAMA Network
