The rate of hospitalizations for kidney disease has risen sharply over the past 25 years, and the elevation has been driven primarily by a significant increase in the proportion of hospitalizations associated with acute renal failure relative to chronic kidney disease, particularly among older Americans, according to the Centers for Disease Control and Prevention.
An analysis of data from a national probability survey showed that the number of patients hospitalized with a diagnosis of either chronic or acute kidney disease rose from 416,000 in 1980 to 1.6 million in 2005, reported Dr. Nicole T. Flowers, a medical epidemiologist at the CDC, and her colleagues. Consistent increases in the rate of acute renal failure over the 25-year period, with smaller increases in the rate of chronic kidney failure, led to the shift in type of kidney disease most commonly associated with hospitalizations. The age-adjusted rate per 10,000 population for hospitalization for acute renal failure increased from 1.8 in 1980 to 36.5 in 2005. During the same period, the rate of chronic kidney failure rose from 7.4 to 13.8 per 10,000 population, they wrote (MMWR 2008;57:309–12).
Other trends emerging from the National Hospital Discharge Survey for 1980–2005 include consistently higher kidney disease hospitalization rates among men compared with women, a rise in the number of patients aged 65 years and older requiring hospitalization for kidney disease, and an increase in the number of kidney disease hospital discharges associated with a concomitant diagnosis of diabetes mellitus or hypertension.
Although the rates of kidney disease for both sexes increased significantly over the 25-year period, “the rates were consistently 30%-40% higher among men than among women,” the authors reported. Hospitalizations increased in all age groups except for individuals younger than 18 years, they wrote, noting: “An increase of approximately 300% (from 56.2 to 179.3 per 10,000 population) occurred among persons aged 65–74 years, and an increase of approximately 350% (from 119.0 to 393.2 per 10,000 population) occurred among persons aged 75 years and older.”
With respect to concomitant diagnoses, diabetes mellitus was reported as an additional discharge diagnosis for 23.4% of hospitalized kidney disease patients in 1980 and for 27.0% in 2005.
“This proportion peaked at 39.0% in 1996,” the authors wrote. The percentage of hospitalized kidney disease patients with a discharge diagnosis of hypertension rose from 19.6% in 1980 to 41.1% in 2005.
In an accompanying editorial, the CDC suggested that the unexplained increase in hospitalizations associated with acute renal failure “might be attributed to actual increases in [acute renal failure] among hospitalized patients or to changes in the way it is diagnosed, defined, or reflected in hospital discharge codes.” It might also be a function, in part, of the aging of the U.S. population, “with greater numbers of older adults having diabetes and hypertension, both of which are major factors and comorbidities for kidney disease.”
The study findings are limited by their basis in medical records, which precludes the assessment of classification validity, particularly for the diagnosis of acute renal failure, because no standardized diagnostic criterion exists, the authors noted. Additionally, the study data are subject to sampling variability and do not allow for race- or ethnicity-based analyses, they said.
Limitations notwithstanding, the findings underscore the need for screening and early detection of kidney disease, as well as the need for standardized diagnostic criteria for acute renal failure, the authors wrote.