Bipolar I (B-I) is an important cause of morbidity and mortality in hospitalized patients. While B-I has been extensively studied in the past, the contemporary data for impact of B-I on cost of hospitalization are largely lacking.

We queried the Healthcare Cost and Utilization Project's Nationwide Inpatient Sample (HCUP-NIS) dataset between 1998–2011 using the ICD-9 codes. Severity of comorbid conditions was defined by Deyo modification of Charlson comorbidity index. Primary outcome was in-hospital mortality and secondary outcome was total charges for hospitalization. Using SAS 9.2, Chi² test, t-test and Cochran-Armitage test were used to test significance.

A total of 1,80,681 were analyzed; 56.29% were female and 43.71% were male (P<0.0001); 70.63% were white, 17.14% black and 12.23% of other race (P<0.0001). Rate of hospitalization increased from 7469.65/million to 9375.27/million from 1998–2011. Overall mortality was 0.12% and mean cost of hospitalization was 19,821.50$. The in-hospital mortality increased from 0.13% to 0.16% (P<0.0001) and mean cost of hospitalization increased from 12,091.31$ to 29,292.97$. Total yearly spending on B-I related admissions increased from $0.72 million/year to $2.16 billion/year.

While mortality has slightly increased from 1998 to 2011, the cost has significantly increased from $0.72 million/year to $2.16 billion/year, which leads to an estimated $1.46 billion/year additional burden to US health care system. In the era of cost conscious care, preventing B-I related Hospitalization could save billions of dollars every year. Focused efforts are needed to establish preventive measures for B-I related hospitalization.