GEOGRAPHY, EXERCISE, AND HOSPITALIZATION RATES IN END STAGE RENAL DISEASE PATIENTS

Background: In the United States, currently more than 650,000 patients suffer from end stage renal disease (ESRD), and require renal replacement therapy (i.e. transplantation or dialysis) to sustain life. With dialysis modalities, the therapy assumes some functions of the diseased kidneys through treatments that occur three times per week to daily. The impact of geography and exercise status on hospitalization rates in ESRD patients has not been well characterized. We aimed to compare the geographical profiles of hospital length of stay in a large national cohort of dialysis patients versus the exercise status reported for the general population. Methods: We analyzed data from the Fresenius Medical Care Knowledge Center on all hemodialysis patients who were treated for > 90 days in 2015. Patients were assigned to a commuting zone (groups of adjacent counties that are defined based on commuting patterns; similar to a metro area) according to their home zip code. The largest 100 commuting zones were selected based on regions with the largest number of ESRD patients. The average annual hospital length of stay in days per patient year (ppy) was calculated for ESRD patients by commuting zone. We further utilized data from CDC Behavioral Risk Factor Surveillance System to analyze the proportion of the general population that exercised in the previous 30 days from the survey date in each commuting zone, stratified by the lowest and highest income quartile. The relationship between the average hospital days ppy and the proportion of the general population who exercised in the same geographical commuting zone was analyzed, and the population-weighted Pearson correlation coefficient (r) between the two variables was calculated using the programming language R. Results: Among 125,534 ESRD patients studied, we observed that the rate of hospital days ppy was distinguishable between differing geographic commuting zones; the rates ranged from about 8 to 22 days ppy depending on geographic location. In the concordant geographic commuting zones, the proportion of the general population that exercised in the last 30 days ranged from 53% to 74% in the lowest income quartile, and 80% to 91% in the highest income quartile. Overall, we found that hospital days ppy in ESRD patients were negatively correlated to the proportion of the general population that exercised in the last 30 days in both the lowest income quartile (r = -0.456) and highest income quartile (r = -0.286). Conclusions: The findings revel that there are remarkable geographical health disparities in hospitalization rates for dialysis patients, as well as in exercise patterns in the general population. Further, the correlation identified suggests that regions that have a larger proportion of the general population exercising may have lower hospitalization rates in ESRD patients. These correlations may have important policy implications when comparing health of specific chronically ill populations. Additional investigations are needed to explain this correlation.