Incidence and contributing factors of dementia among people living with HIV in British Columbia, Canada, from 2002 to 2016: a retrospective cohort study.

Introduction: Dementia is a progressive and debilitating disease, and people living with HIV (PLWH) often develop dementia much earlier than those not living with HIV. We estimated the incidence and prevalence of dementia and identified its key risk factors in a cohort of PLWH in British Columbia, Canada.

Methods: This retrospective cohort study used data from the Seek and Treat for Optimal Prevention of HIV/AIDS study. Eligible individuals were diagnosed with HIV, ≥40 years of age, naïve to antiretroviral therapy (ART), had no dementia at the index date and were followed for ≥1 year during 2002-2016. Our main outcome was incident dementia. We examined the effect of sociodemographic and clinical covariates on the incidence of dementia using a cause-specific hazard (CSH) model, with all-cause mortality as a competing risk event.

Results: Among 5121 eligible PLWH, 108 (2%) developed dementia. The crude 15-year prevalence of dementia was 2.1%, and the age-sex standardised incidence rate of dementia was 4.3 (95% CI: 4.2 to 4.4) per 1000 person-years. Among the adjusted covariates, CD4 cell count<50 cells/mm (adjusted CSH (aCSH) 8.61, 95% CI: 4.75 to 15.60), uncontrolled viremia (aCSH 1.95, 95% CI: 1.20 to 3.17), 10-year increase in age (aCSH 2.41, 95% CI: 1.89 to 3.07), schizophrenia (aCSH 2.85, 95% CI: 1.69 to 4.80), traumatic brain injury (aCSH 2.43, 95% CI: 1.59 to 3.71), delirium (aCSH 2.27, 95% CI: 1.45 to 3.55), substance use disorder (SUD) (aCSH 1.94, 95% CI: 1.18 to 3.21) and mood/anxiety disorders (aCSH 1.80, 95% CI: 1.13 to 2.86) were associated with an increased hazard for dementia. Initiating ART in 2005-2010 (versus<2000) produced an aCSH of 0.51 (95% CI: 0.30 to 0.89).

Conclusions: We demonstrated the negative role of immunosuppression and inflammation on the incidence of dementia among PLWH. Our study also calls for the enhanced integration of care services provided for HIV, mental health, SUD and other risk-inducing comorbidities as a means of lowering the risk of dementia within this population.