Severe Acute Kidney Injuries Double in 10 Years

Joe Barber Jr, PhD

December 11, 2012

Researchers estimate that the incidence of severe, dialysis-requiring acute kidney injury (AKI) and the number of resulting deaths more than doubled during a recent 10-year period.

Raymond K. Hsu, MD, from the Department of Medicine, University of California, San Francisco, and colleagues report their findings in an article published online December 6 in the Journal of the American Society of Nephrology.

The authors note that the incidence of AKI has remained unclear despite its importance. "Prior studies have expressed AKI incidence as cases per hospitalization or per intensive care unit stay, making comparisons across regions and over time difficult to interpret, because thresholds for admission may vary," the authors write. "Few studies have studied AKI incidence as case per underlying population, and recent temporal trends in the US population incidence are not well defined."

In the current study, the authors extracted 2000 to 2009 data from the National Inpatient Sample to identify cases of dialysis-requiring AKI, using validated International Classification of Diseases, Ninth Edition, codes. The population incidence rate of dialysis-requiring AKI more than doubled, going from 222 cases/million person-years in 2000 to 533 cases/million person-years in 2009, resulting in an incidence rate ratio of 1.10 (95% confidence interval [CI], 1.10 - 1.11).

Subgroup analysis was performed for age, sex, and race, and logistic regression analysis was performed with adjustments for age, sex, race, acute heart failure, cardiac catheterization, and mechanical ventilation. Subgroup analysis revealed that the elderly (compared with younger age groups), men (compared with women), and non-Hispanic blacks (compared with non-Hispanic whites) were more likely to develop dialysis-requiring AKI.

Although the inpatient fatality rate declined from 29.1% to 23.5% between 2000 and 2009, the number of deaths more than doubled, going from 18,000 to nearly 39,000 during the same period.

In univariate regression analysis, the odds of developing dialysis-requiring AKI increased by 10.1% per year (odds ratio, 1.10; 95% CI, 1.09 - 1.11; P < .001). After adjustment for the aforementioned variables, the odds ratio was reduced to 1.07 (95% CI, 1.06 - 1.07; P < .001). The authors note that similar trends were observed in all examined subgroups.

"In summary, we found that population incidence of dialysis-requiring AKI has increased rapidly at 10% annually using a nationally representative sample of hospitalizations," they conclude. "Our findings are consistent with and extend on older studies showing an increase in disease incidence in the United States over time."

The researchers note, however, that the reasons for the increase are unclear.

The authors have disclosed no relevant financial relationships.

J Am Soc Nephrol. Published online December 6, 2012. Abstract