medwireNews: Individuals whose cannabis use leads to hospital-based care or emergency room visits may be at increased risk for dementia compared with people with non-cannabis-related acute care encounters and the general population, suggests a study published in JAMA Neurology.
“Cannabis use is associated with structural brain changes and short-term memory problems,” yet little is known about the impact “disordered cannabis use” has on the risk for dementia, observe the study authors. They found that annual cannabis-related acute care encounters in Ontario, Canada, increased 5.4-fold between 2008 and 2012 in people aged 45–64 years and 26.7-fold in those 65 years and older.
Daniel Myran (Ottawa Hospital Research Institute) and colleagues assessed dementia risk in 6,086,794 individuals aged 45 to 105 years with no history of dementia, 16,275 of whom received acute care for cannabis use either at hospital or in the emergency department. They were a mean 55.2 years of age and 60.3% were men.
At 5 years, 5.0% of 15,120 members of this latter group had dementia compared with 3.6% of 125,704 individuals matched for age and sex who had incident acute care for reasons other than cannabis use. Similarly, when the full group of 16,275 individuals who received acute care for cannabis use was compared with 156,473 age- and sex-matched members of the general population, the rates of dementia diagnoses at 5 years were 5.0% and 1.3%, respectively.
This translated to significant 1.5-fold and 3.9-fold increases in dementia risk for patients in the cannabis-related acute care group, respectively, and 1.2-fold and 1.72-fold increases after further adjustment for sociodemographic characteristics, prior substance use, mental healthcare, and the presence of comorbid chronic conditions.
However, the risk for dementia in the cannabis-related acute care group was significantly lower than that of 119,163 individuals who received acute care for alcohol-related reasons, at 5.0% versus 8.0%, with an age- and sex-adjusted hazard ratio (HR) of 0.76 and a fully adjusted HR of 0.69.
At the 10-year mark, 18.6% of those who received acute care due to cannabis use were diagnosed with dementia, compared with 14.9% of those in the non-cannabis-related acute care group, 5.5% of the general population, and 21.7% of those in the alcohol-related acute care group.
Myran and team note that the significantly increased risks for dementia at 5 and 10 years in those receiving acute care for cannabis use were similar in men and women, although acute care for cannabis use was more common in men.
In secondary analyses, cannabis-related acute care was also associated with significantly increased risks for delirium and early-onset dementia but only when compared with the general population (adjusted HR=2.26 and 2.04, respectively).
The investigators say that “[a]lthough the associations reported in our study should not be interpreted as causal, it is relevant to consider potential mechanisms in which regular cannabis use might increase the risk of dementia.”
They note that “[l]ong-term cannabis use has been associated with memory and attention problems in midlife along with declines in hippocampal volume, which are both associated with dementia.”
The study authors conclude that “regardless of causality, our findings have clinical implications highlighting a group at high risk of developing dementia who may benefit from close follow-up and intervention or preventive efforts.”
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