SMOKING STATUS AND HOSPITALIZATION RATES IN DIALYSIS PATIENTS IN DIFFERING GEOGRAPHIES

Background: The detrimental effects of tobacco smoking are well documented in the general population. However, studies on its impact on end stage renal disease (ESRD) patients are scarce. ESRD affects 650,000 Americans, and refers to the last stage of chronic kidney disease where the kidneys cannot function adequately. Patients with ESRD require either a kidney transplant, or dialysis to live. The influence of geographic location and cigarette smoking on hospitalization rates in ESRD patients has not been analyzed. We thus compared the geographical profiles of hospital length of stay in a national cohort of hemodialysis (HD) patients versus the smoking status reported for the general population. Methods: We analyzed data from the Fresenius Medical Care Knowledge Center on all HD patients treated in 2015, and who survived at least 90 days of treatment. 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, and the largest 100 commuting zones were selected based on regions with the largest number of HD patients. The average annual hospital length of stay in days per patient year (ppy) was calculated for HD patients by commuting zone. We gathered data from The CDC Behavioral Risk Factor Surveillance System to study the fraction of smokers in the general population stratified by the lowest and highest income quartiles in each geographical area. The relationship between the average hospital days ppy and the fraction of current smokers in the general population within the same commuting zone was analyzed, and the population-weighted Pearson correlation coefficient (r) was calculated using programming language R. Results: Among 125,534 HD patients studied, several observations were appreciated: i) there were differences in the rate of hospital days ppy among geographical areas, varying from 7 to 22 days ppy. ii) The fraction of smokers in the general population ranged from 14% to 35% in the lowest income quartile (mostly between 20% and 35%), and 8.5% to 21% in the highest income quartile (mostly between 8.5% and 18%). iii) Hospital days ppy in HD patients were positively correlated to the fraction of smokers in the general population in both the lowest (r = 0.304) and highest (r = 0.386) income quartiles. Conclusions: Our findings show there are notable geographical differences in hospitalization rates for HD patients and percentages of smokers in the general population. The correlation identified indicates that longer hospital stay may be observed in ESRD patients in regions with a larger proportion of smokers. Nonetheless, further studies are necessary to support these observations and understand the presented correlations.