Introduction: In patients with chronic kidney disease (CKD), studies investigating the association between smoking and deterioration of kidney function are scarce. Aims and Methods: We analyzed data for 1,951 patients with an estimated glomerular filtration rate (eGFR) ≥15 mL/min/1.73 m2 enrolled in the KoreaN cohort study for Outcome in patients With Chronic Kidney Disease (KNOW-CKD) from 2011 to 2016. Patients were categorized by smoking load. Primary outcome was a composite of a ≥50% reduction in eGFR, initiation of dialysis, or kidney transplantation. Results: There were 967 never-smokers and 369, 276, and 339 smokers who smoked <15, 15 to 29, ≥30 pack-years, respectively. During a mean follow-up of 3.0 years, the incidence rates (95% confidence interval [CI]) of the primary outcome were 54.3 (46.4–63.5), 46.9 (35.9–61.4), 69.2 (52.9–90.6), and 76.3 (60.7–96.0) events per 1,000 person-yr in never-, <15, 15 to 29, and ≥30 pack-year smokers. In cause-specific hazard model after adjustment of confounding factors, smokers were associated with 1.09 (0.73–1.63), 1.48 (1.00–2.18), and 1.94 (1.35–2.77) fold increased risk (95% CI) of primary outcome in <15, 15–29, and ≥30 pack-year smokers compared with never-smokers. The association of longer smoking duration with higher risk of CKD progression was evident particularly in patients with eGFR < 45 mL/min/1.73 m2 and proteinuria ≥ 1.0 g/g. In contrast, the risk of adverse kidney outcome decreased with longer smoking-free periods among former-smokers. Conclusions: These findings suggest potentially harmful effects of the degree of exposure to smoking on the progression of CKD. Implications: Among patients with CKD, there has been lack of studies on the association between smoking and CKD progression and studies to date have yielded conflicting results. In this prospective cohort study involving Korean CKD patients, smoking was associated with significantly higher risk of worsening kidney function. Furthermore, the risk of adverse kidney outcome was incrementally higher as smoking pack-years were higher. As the duration of smoking cessation increased, the hazard ratios for adverse kidney outcome were attenuated, suggesting that quitting smoking may be a modifiable factor to delay CKD progression.

Background: High‐density lipoprotein cholesterol ( HDL ‐C) levels are generally decreased in patients with chronic kidney disease ( CKD ). However, studies on the relationship between HDL ‐C and CKD progression are scarce. Methods and Results: We studied the association between serum HDL ‐C levels and the risk of CKD progression in 2168 participants of the KNOW ‐ CKD (Korean Cohort Study for Outcome in Patients With Chronic Kidney Disease). The primary outcome was the composite of a 50% decline in estimated glomerular filtration rate from baseline or end‐stage renal disease. The secondary outcome was the onset of end‐stage renal disease. During a median follow‐up of 3.1 (interquartile range, 1.6–4.5) years, the primary outcome occurred in 335 patients (15.5%). In a fully adjusted Cox model, the lowest category with HDL ‐C of <30 mg/dL (hazard ratio, 2.21; 95% CI, 1.30–3.77) and the highest category with HDL ‐C of ≥60 mg/dL (hazard ratio, 2.05; 95% CI , 1.35–3.10) were associated with a significantly higher risk of the composite renal outcome, compared with the reference category with HDL ‐C of 50 to 59 mg/dL. This association remained unaltered in a time‐varying Cox analysis. In addition, a fully adjusted cubic spline model with HDL ‐C being treated as a continuous variable yielded similar results. Furthermore, consistent findings were obtained in a secondary outcome analysis for the development of end‐stage renal disease. Conclusions: A U‐shaped association was observed between serum HDL ‐C levels and adverse renal outcomes in this large cohort of patients with CKD . Our findings suggest that both low and high serum HDL ‐C levels may be detrimental to patients with nondialysis CKD .

Background and objectives Active smoking is associated with higher risk of various diseases. However, the risk of CKD development in nonsmokers exposed to secondhand smoke is not well elucidated. We aimed to investigate the association between secondhand smoke exposure and the risk of CKD development among never-smokers. Design, setting, participants, & measurements A total of 131,196 never-smokers with normal kidney function, who participated in the Korean Genome and Epidemiology Study from 2001 to 2014, were analyzed. The participants were classified into three groups on the basis of frequency of secondhand smoke exposure, assessed with survey questionnaires; no exposure, <3 days per week, and ≥3 days per week. The association between secondhand smoke and CKD, defined as eGFR<60 ml/min per 1.73 m², was examined in the cross-sectional analysis. In addition, the risk of incident CKD development was analyzed in a longitudinal cohort of 1948 participants without CKD at baseline, which was a subset of the main cohort. Results The mean age of participants was 53 years, and 75% were women. Prevalent CKD was observed in 231 (1.8%), 64 (1.7%), and 2280 (2.0%) participants in the ≥3 days per week, <3 days per week, and no exposure groups. The odds ratio (OR) of prevalent CKD was significantly higher in the groups exposed to secondhand smoke than the no exposure group (<3 days per week: OR, 1.72; 95% confidence interval [95% CI], 1.30 to 2.27; and ≥3 days per week: OR, 1.44; 95% CI, 1.22 to 1.70). During a mean follow-up of 104 months, CKD occurred in 319 (16%) participants. Multivariable Cox analysis revealed that the risk for CKD development was higher in participants exposed to secondhand smoke than the no exposure group (<3 days per week: hazard ratio, 1.59; 95% CI, 0.96 to 2.65; and ≥3 days per week: hazard ratio, 1.66; 95% CI, 1.03 to 2.67). Conclusions Exposure to secondhand smoke was associated with a higher prevalence of CKD as well as development of incident CKD. Visual Abstract

Despite the importance of preventing chronic kidney disease (CKD), predicting high-risk patients who require active intervention is challenging, especially in people with preserved kidney function. In this study, a predictive risk score for CKD (Reti-CKD score) was derived from a deep learning algorithm using retinal photographs. The performance of the Reti-CKD score was verified using two longitudinal cohorts of the UK Biobank and Korean Diabetic Cohort. Validation was done in people with preserved kidney function, excluding individuals with eGFR <90 mL/min/1.73 m² or proteinuria at baseline. In the UK Biobank, 720/30,477 (2.4%) participants had CKD events during the 10.8-year follow-up period. In the Korean Diabetic Cohort, 206/5014 (4.1%) had CKD events during the 6.1-year follow-up period. When the validation cohorts were divided into quartiles of Reti-CKD score, the hazard ratios for CKD development were 3.68 (95% Confidence Interval [CI], 2.88–4.41) in the UK Biobank and 9.36 (5.26–16.67) in the Korean Diabetic Cohort in the highest quartile compared to the lowest. The Reti-CKD score, compared to eGFR based methods, showed a superior concordance index for predicting CKD incidence, with a delta of 0.020 (95% CI, 0.011–0.029) in the UK Biobank and 0.024 (95% CI, 0.002–0.046) in the Korean Diabetic Cohort. In people with preserved kidney function, the Reti-CKD score effectively stratifies future CKD risk with greater performance than conventional eGFR-based methods.