Effects of residential greenness on clinical outcomes of patients with chronic kidney disease: a large-scale observation study

Abstract

Background As industrialization and urbanization are accelerating, the distribution of green areas is decreasing, particularly in developing countries. Since the 2000s, the effects of surrounding greenness on self-perceived health, including physical and mental health, longevity, and obesity have been reported. However, the effects of surrounding green space on chronic kidney disease are not well understood. Therefore, we investigated the impact of residential greenness on the mortality of chronic kidney disease patients and progression from chronic kidney disease to end-stage renal disease (ESRD). Methods Using a large-scale observational study, we recruited chronic kidney disease patients (n = 64,565; mean age, 54.0 years; 49.0% of male) who visited three Korean medical centers between January 2001 and December 2016. We investigated the hazard ratios of clinical outcomes per 0.1-point increment of exposure to greenness using various models. Results During the mean follow-up of 6.8 ± 4.6 years, 5,512 chronic kidney disease patients developed ESRD (8.5%) and 8,543 died (13.2%). In addition, a 0.1-point increase in greenness reduced all-cause mortality risk in chronic kidney disease and ESRD patients and progression of chronic kidney disease to ESRD in a fully adjusted model. The association between mortality in ESRD patients and the normalized difference vegetation index was negatively correlated in people aged >65 years, who had normal weight, were nonsmokers, and lived in a nonmetropolitan area. Conclusion Chronic kidney disease patients who live in areas with higher levels of greenness are at reduced risk of all-cause mortality and progression to ESRD.

Greenness and kidney? A review of epidemiological studies on the association between green space and kidney disease

“…Korean studies based on the National Health Insurance System also showed that exposure to heat and air pollutants increases hospital admissions related to kidney disease [ 16 , 33 ]. Furthermore, previous studies suggested that the beneficial effects of green space on cardiovascular diseases [ 12 , 34 ], which are major causes of kidney diseases, should be majorly addressed in the beneficial roles of greenness on kidney health [ 19 , 25 ]. These results from multiple studies support biological mechanisms and epidemiological evidence of the beneficial effects of greenness on kidney health.…”

“…James et al [ 23 ] designed the study to examine the association between green space and various causes of mortality, not only for kidney disease-related deaths. The cohort study of Park et al [ 25 ] was based on a large-scale prospective cohort, but covered patients enrolled at metropolitan hospitals, thus there were limitations in addressing nonmetropolitan areas, particularly rural areas which are generally more vulnerable to medical services [ 36 ]. Paoin et al [ 28 ] also conducted a prospective cohort study; however, their study included only employees in a certain company with limited age distribution (25 to 55 years), thus the generalizability of the study result may be less than in other population-based or multilocation cohort studies.…”

“…Furthermore, we should note that different buffer sizes to measure NDVI can increase the uncertainty of association assessment. Studies in this review used different buffer sizes: 250 m, 1,250 m [ 23 , 25 ], and 1,000 m [ 26 ]; and the evaluated association between greenspace and kidney outcomes was not robust to the buffer sizes [ 25 ]. Therefore, various sensitivity analyses and further studies to find the optimal greenness index and buffer sizes are required.…”

“…Fourth, potentially different exposure levels and health effects of green space depending on socioeconomic characteristics should be addressed importantly in future studies. Many studies in this review were performed in urban areas [ 24 , 25 , 27 , 28 ], thus there is a knowledge gap in explaining whether the beneficial effects of green space exist in rural areas. In addition, urbanicity is closely related to socioeconomic and environmental status as well as demographic compositions [ 40 ].…”

“…In 2021, a multihospital-based prospective cohort study in South Korea examined the association between residential greenness and clinical outcomes of CKD patients [ 25 ]. The study constructed a large-scale cohort including 64,565 patients diagnosed with CKD from multiple metropolitan hospitals, and an average NDVI during the summer (June to August) corresponding to each participant’s residential address was used as an exposure to green space.…”