The incidence of cardiovascular morbidity among patients with bipolar disorder: a population-based longitudinal study in Ontario, Canada.

BACKGROUND

Despite the high rates of cardiovascular risk factors among people with bipolar disorder, little is known about the incidence of cardiovascular morbidity in this population.

METHODS

Based upon Ontario, Canada hospital discharge records from April 1, 2002 to March 31, 2006, we constructed a population-based cohort study to assess whether individuals diagnosed with bipolar disorder (n=5999) would have a significantly greater risk of subsequent readmission with a cardiovascular condition in comparison to a matched population-proxy group of individuals receiving an appendicitis primary diagnosis. A Cox regression procedure was used to estimate group differences in time-to-readmission with a cardiovascular-related diagnosis. Patients were followed for a period up to 4 years.

RESULTS

The bipolar disorder group had a significantly greater adjusted risk of readmission for a cardiovascular event in comparison to individuals in the appendicitis group [adjusted hazard ratio (AHR)=1.66, 95% CI, 1.37-2.07, p<0.001).

LIMITATIONS

Current research has not confirmed the accuracy of ICD-10 bipolar diagnoses in population-based administrative files with a gold-standard diagnostic reference. Also, our study did not have access to mortality files which, given the elevated rate of mortality among patients with bipolar disorder, may have led to an underestimation of link between bipolar disorder and cardiovascular morbidity.

CONCLUSIONS

In light of the elevated risk of cardiovascular morbidity among persons with bipolar disorder, our findings add to the importance of screening and intervention programs for metabolic disorders and known cardiovascular risk factors among patients with bipolar disorder.