Associations between off-label low-dose olanzapine or quetiapine and cardiometabolic mortality

Olanzapine and quetiapine are routinely used off-label at lower doses, though it remains unclear whether treatment is associated with mortality. Here, we examined the associations between low-dose olanzapine/quetiapine, defined as 5 mg/day of olanzapine equivalents (OE) with cardiometabolic mortality in a population-based, longitudinal cohort of individuals who sought specialized psychiatric services. Through cross-linked Swedish registries, 428,525 individuals without psychotic, bipolar, or cardiometabolic disorders, or previous treatment with antipsychotics or cardiometabolic-related drugs were followed for up to 10.5 years. Extended stratified Cox proportional hazards regressions were employed to estimate the hazard ratios (HR) of cardiometabolic mortality as a function of cumulative OE exposures, adjusted for age, sex, inpatient care, and time-dependent psychiatric diagnoses and treatments. Individuals were followed for a total of 2.1 million person-years. Treatment with olanzapine/quetiapine occurred in 18,317 of the cohort. In total, 2606 cardiometabolic-related deaths occurred. Treatment status (treated vs. untreated) was not significantly associated with cardiometabolic mortality (adjusted HR 0.86, 95% CI 0.64–1.15, P = 0.307). However, compared to no treatment, treatment for <6 months was significantly associated with a reduced risk (adjusted HR 0.56, 95% CI 0.37–0.87, P = 0.010) whereas treatment for 6–12 months was significantly associated with an increased risk (adjusted HR 1.89, 95% CI 1.22–2.92, P = 0.004), but not significantly beyond 12 months. Among those treated, each year exposed to an average 5 mg/day was significantly associated with increased cardiometabolic mortality (adjusted HR 1.45, 95% CI 1.06–1.99, P = 0.019). Overall, low-dose olanzapine/quetiapine treatment was weakly associated with cardiometabolic mortality. Clinicians should consider potential cardiometabolic sequelae at lower doses.