Short-term Blood Pressure Variability and Incident CKD in Patients With Hypertension: Findings From the Cardiovascular and Metabolic Disease Etiology Research Center-High Risk (CMERC-HI) Study.

RATIONALE & OBJECTIVE: The association between short-term blood pressure variability (BPV) and kidney outcomes is poorly understood. This study evaluated the association between short-term BPV and kidney disease outcomes in people with hypertension. STUDY DESIGN: Prospective observational cohort study. SETTING & PARTICIPANTS: 1,173 hypertensive participants in the Cardiovascular and Metabolic Disease Etiology Research Center-High Risk (2013-2018) Study with estimated glomerular filtration rate (eGFR) ≥60mL/min/1.73m2. EXPOSURE: Short-term BPV assessed by average real variability (ARV). OUTCOME: Composite kidney disease outcome (30% decline in eGFR from baseline, new occurrence of eGFR <60mL/min/1.73m2, or onset of UACR >300mg/g). ANALYTICAL APPROACH: Multivariable Cox regression analyses to evaluate the association between systolic and diastolic BP ARV (SBP-ARV and DBP-ARV) and outcomes. RESULTS: During a median follow-up of 5.4 [4.1-6.5] years, 271 events of the composite kidney disease outcome occurred (46.5 per 1,000 person-years). Multivariable Cox analysis revealed that the highest SBP-ARV and DBP-ARV tertiles were associated with a higher risk of the composite kidney disease outcome than the lowest tertiles, independent of the 24-hour SBP or DBP levels (HR, 1.64 [95% CI, 1.16-2.33], and 1.60 [95% CI, 1.15-2.24] for SBP-ARV and DBP-ARV, respectively). These associations were consistent when SBP-ARV and DBP-ARV were treated as continuous variables (HR per 1.0-unit greater SBP-ARV, 1.03 [95% CI, 1.01-1.06]; HR per 1.0-unit greater DBP-ARV, 1.04 [95% CI, 1.01-1.08]). These associations were consistent, irrespective of subgroups (age, sex, 24-hour SBP or DBP, and moderate albuminuria). However, other measures of short-term BPV including SD, coefficient of variation, and dipping patterns were not associated with the composite kidney disease outcome. LIMITATIONS: Observational study design, the use of single measurement of 24-hour BP, lack of information on changes in antihypertensive medication during the follow-up. CONCLUSIONS: Short-term BPV is associated with the development of a composite kidney disease outcome in hypertensive patients.

Association Between Ultraprocessed Food Consumption and Risk of Incident CKD: A Prospective Cohort Study.

RATIONALE & OBJECTIVE: Ultraprocessed foods have become readily available in the global food supply in the past few decades. Several adverse health outcomes have been linked with higher consumption of ultraprocessed foods. However, the impact of ultraprocessed foods on chronic kidney disease (CKD) risk remains unknown. STUDY DESIGN: Prospective cohort study. SETTING & PARTICIPANTS: 14,679 middle-aged adults without CKD at baseline in the Atherosclerosis Risk in Communities (ARIC) study. EXPOSURE: Ultraprocessed foods consumption (servings per day) calculated using dietary data collected via a food frequency questionnaire at visit 1 and visit 3. OUTCOME: Incident CKD defined as estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m2 accompanied by ≥25% eGFR decline, CKD-related hospitalization or death, or kidney failure with kidney replacement therapy. ANALYTICAL APPROACH: Multivariable-adjusted Cox proportional hazards models were used to assess the association between ultraprocessed foods consumption and CKD. Restricted cubic splines were used to examine the shape of the association. RESULTS: During a median follow-up period of 24 years, there were 4,859 cases of incident CKD. The incidence rate for the highest quartile of ultraprocessed foods consumption was 16.5 (95% CI, 15.6-17.4) per 1,000 person-years and 14.7 (95% CI, 13.9-15.5) per 1,000 person-years for the lowest quartile of consumption. After adjusting for a range of confounders including lifestyle factors, demographic characteristics, and health behaviors, participants in the highest quartile of ultraprocessed foods consumption had a 24% higher risk (HR, 1.24 [95% CI, 1.15-1.35]) of developing CKD compared with those in the lowest quartile. There was an approximately linear relationship observed between ultraprocessed food intake and risk of CKD. By substituting 1 serving of ultraprocessed foods with minimally processed foods, there was a 6% lower risk of CKD observed (HR, 0.94 [95% CI, 0.93-0.96]; P < 0.001). LIMITATIONS: Self-reported data and residual confounding. CONCLUSIONS: Higher ultraprocessed foods consumption was independently associated with a higher risk of incident CKD in a general population.

Association of Long-term Ambient Fine Particulate Matter (PM2.5) and Incident CKD: A Prospective Cohort Study in China.

RATIONALE & OBJECTIVE: Increasing evidence has linked ambient fine particulate matter (ie, particulate matter no larger than 2.5 µm [PM2.5]) to chronic kidney disease (CKD), but their association has not been fully elucidated, especially in regions with high levels of PM2.5 pollution. This study aimed to investigate the long-term association of high PM2.5 exposure with incident CKD in mainland China. STUDY DESIGN: Prospective cohort study. SETTING & PARTICIPANTS: 72,425 participants (age ≥18 years) without CKD were recruited from 121 counties in Hunan Province, China. EXPOSURE: Annual mean PM2.5 concentration at the residence of each participant derived from a long-term, full-coverage, high-resolution (1 × 1 km2), high-quality dataset of ground-level air pollutants in China. OUTCOMES: Incident CKD during the interval between the baseline examination of each participant (2005-2017) and the end of follow-up through 2018. ANALYTICAL APPROACH: Cox proportional hazards models were used to estimate the independent association of PM2.5 with incident CKD and the joint association of PM2.5 with temperature or humidity on the development of PM2.5-related CKD. Restricted cubic splines were used to model exposure-response relationships. RESULTS: Over a median follow-up of 3.79 (IQR, 2.03-5.48) years, a total of 2,188 participants with incident CKD were identified. PM2.5 exposure was associated with incident CKD with an adjusted hazard ratio of 1.71 (95% CI, 1.58-1.85) per 10-µg/m3 greater long-term exposure. Multiplicative interactions between PM2.5 and humidity or temperature on incident CKD were detected (all P < 0.001 for interaction), whereas an additive interaction was detected only for humidity (relative risk due to interaction, 3.59 [95% CI, 0.97-6.21]). LIMITATIONS: Lack of information on participants' activity patterns such as time spent outdoors. CONCLUSIONS: Greater long-term ambient PM2.5 pollution is associated with incident CKD in environments with high PM2.5 exposure. Ambient humidity has a potentially synergetic effect on the association of PM2.5 with the development of CKD. PLAIN-LANGUAGE SUMMARY: Exposure to a form of air pollution known as fine particulate matter (ie, particulate matter ≤2.5 µm [PM2.5]) has been linked to an increased risk of chronic kidney disease (CKD), but little is known about how PM2.5 affects CKD in regions with extremely high levels of PM2.5 pollution. This longitudinal cohort study in China investigates the effect of PM2.5 on the incidence of CKD and whether temperature or humidity interact with PM2.5. Our findings suggest that long-term exposure to high levels of ambient PM2.5 significantly increased the risk of CKD in mainland China, especially in terms of cumulative average PM2.5. The associations of PM2.5 and incident CKD were greater in high-humidity environments. These findings support the recommendation that reducing PM2.5 pollution should be a priority to decrease the burden of associated health risks, including CKD.

Obesity Without Metabolic Abnormality and Incident CKD: A Population-Based British Cohort Study.

RATIONALE & OBJECTIVE: Metabolically healthy obesity (obesity without any metabolic abnormality) is not considered to be associated with increased risk of morbidity and mortality. We examined and quantified the association between metabolically healthy overweight/obesity and the risk of incident chronic kidney disease (CKD) in a British primary care population. STUDY DESIGN: Retrospective population-based cohort study. SETTING & PARTICIPANTS: 4,447,955 of the 5,182,908 adults in The Health Improvement Network (THIN) database (United Kingdom, 1995-2015) with a recorded body mass index (BMI) at the time of registration date who were free of CKD and cardiovascular disease. EXPOSURE: 11 body size phenotypes were created, defined by BMI categories (underweight, normal weight, overweight, and obesity) and 3 metabolic abnormalities (diabetes, hypertension, and dyslipidemia). OUTCOME: Incident CKD defined as a recorded code for kidney replacement therapy, a recorded diagnosis of CKD, or by an estimated glomerular filtration rate of<60mL/min/1.73m2 for≥90 days, or a urinary albumin-creatinine ratio>3mg/mmol for≥90 days. RESULTS: Of the 4.5 million individuals, 1,040,921 (23.4%) and 588,909 (13.2%) had metabolically healthy overweight and metabolically healthy obesity, respectively. During a mean follow-up interval of 5.4±4.3 (SD) years, compared with individuals with a metabolically healthy normal weight (n=1,656,231), there was a higher risk of incident CKD among those who had metabolically healthy overweight (adjusted HR, 1.30 [95% CI, 1.28-1.33]) and metabolically healthy obesity (adjusted HR, 1.66 [95% CI, 1.62-1.70]). The association was stronger in those younger than 65 years of age. In all BMI categories, there was greater risk of incident CKD with a greater number of metabolic abnormalities in a graded manner. LIMITATIONS: Potential misclassification of metabolic status due to delayed diagnosis and residual confounding due to unmeasured factors. CONCLUSIONS: Overweight and obesity without metabolic abnormality are associated with a higher risk of incident CKD compared with those with normal body weight and no metabolic abnormality.

Serum matrix metalloproteinase 7 and accelerated glomerular filtration rate decline in a general non-diabetic population.

BACKGROUND: Age-related reduction of glomerular filtration rate (GFR) is a major contributor to the global chronic kidney disease (CKD) epidemic. We investigated whether baseline serum levels of the pro-fibrotic matrix metalloproteinase 2 (MMP2), MMP7 and their inhibitor, tissue inhibitor of metalloproteinase 1 (TIMP1), which mediates fibrosis development in aging animals, were associated with GFR decline in a general non-diabetic population. METHODS: In the Renal Iohexol Clearance Survey, we measured GFR using iohexol clearance in 1627 subjects aged 50-64 years without self-reported diabetes, kidney or cardiovascular disease. After a median of 5.6 years, 1324 had follow-up GFR measurements. Using linear mixed models and logistic regression analyses, we evaluated the association of MMP7, MMP2 and TIMP1 with the mean GFR decline rate, risk of accelerated GFR decline (defined as subjects with the 10% steepest GFR slopes: ≥1.8 mL/min/1.73 m2/year) and incident CKD [GFR <60 mL/min/1.73 m2 and/or urinary albumin to creatinine ratio (ACR) ≥3.0 mg/mmol]. RESULTS: Higher MMP7 levels (per standard deviation increase of MMP7) were associated with steeper GFR decline rates [-0.23 mL/min/1.73 m2/year (95% confidence interval -0.34 to -0.12)] and increased risk of accelerated GFR decline and incident CKD [odds ratios 1.58 (1.30-1.93) and 1.45 (1.05-2.01), respectively, in a model adjusted for age, sex, baseline GFR, ACR and cardiovascular risk factors]. MMP2 and TIMP1 showed no association with GFR decline or incident CKD. CONCLUSIONS: The pro-fibrotic biomarker MMP7, but not MMP2 or TIMP1, is associated with increased risk of accelerated GFR decline and incident CKD in middle-aged persons from the general population.

Association Between Midlife Physical Activity and Incident Kidney Disease: The Atherosclerosis Risk in Communities (ARIC) Study.

RATIONALE & OBJECTIVE: Physical activity is associated with lower risk for cardiovascular disease, diabetes, and hypertension, which have shared risk factor profiles with chronic kidney disease (CKD). However, there are conflicting findings regarding the relationship between physical activity and CKD. The objective was to evaluate the association between physical activity and CKD development over long-term follow-up using the Atherosclerosis Risk in Communities (ARIC) Study. STUDY DESIGN: Prospective cohort study. SETTING & PARTICIPANTS: 14,537 participants aged 45 to 64 years. PREDICTORS: Baseline physical activity status was assessed using the modified Baecke Physical Activity Questionnaire at visit 1 (1987-1989) and categorized according to the 2018 Physical Activity Guidelines for Americans to group participants as inactive, insufficiently active, active, and highly active. OUTCOMES: Incident CKD defined as estimated glomerular filtration rate (eGFR)<60mL/min/1.73m2 at follow-up and≥25% decline in eGFR relative to baseline, CKD-related hospitalization or death, or initiation of kidney replacement therapy. ANALYTICAL APPROACH: Cox proportional hazards regression. RESULTS: At baseline, 37.8%, 24.2%, 22.7%, and 15.3% of participants were classified as inactive, insufficiently active, active, and highly active, respectively. During a median follow-up of 24 years, 33.2% of participants developed CKD. After adjusting for age, sex, race-center, education, smoking status, diet quality, diabetes, coronary heart disease, hypertension, antihypertensive medication, body mass index, and baseline eGFR, higher categories of physical activity were associated with lower risk for CKD compared with the inactive group (HRs for insufficiently active, 0.95 [95% CI, 0.88-1.02]; active, 0.93 [95% CI, 0.86-1.01]; highly active, 0.89 [95% CI, 0.81-0.97]; P for trend = 0.007). LIMITATIONS: Observational design and self-reported physical activity that was based on leisure time activity only. Due to low numbers, participants who were not Black or White were excluded. CONCLUSIONS: Highly active participants had lower risk for developing CKD compared with inactive participants.

Associations of Systolic Blood Pressure With Incident CKD G3-G5: A Cohort Study of South Korean Adults.

RATIONALE & OBJECTIVE: Clinical practice guidelines recommend a target blood pressure (BP)<130/80 mm Hg to reduce cardiovascular risk. However, the optimal BP to prevent chronic kidney disease (CKD) is unknown. STUDY DESIGN: Population-based retrospective cohort study. SETTING & PARTICIPANTS: 10.5 million adults who participated in the National Health Insurance Service National Health Checkup Program in South Korea between 2009 and 2015 and had an estimated glomerular filtration rate (GFR) ≥ 60 mL/min/1.73 m2 at the beginning of follow-up. PREDICTORS: Baseline and time-updated systolic BP (SBP) as a continuous variable and categorized as<110, 110 to 119, 120 to 129, 130 to 139, or≥140 mm Hg. OUTCOME: Incident CKD GFR categories 3 to 5 (CKD G3-G5), defined as de novo development of estimated GFR<60 mL/min/1.73 m2 for at least 2 consecutive assessments confirmed at least 90 days apart. ANALYTICAL APPROACH: Cox proportional hazards regression for baseline BP and marginal structural analysis for time-updated BP. RESULTS: During 49,169,311 person-years of follow-up, incident CKD G3-G5 developed in 172,423 (1.64%) individuals with a crude event rate of 3.51 (95% CI, 3.49-3.52) per 1,000 person-years. Compared to a baseline SBP of 120 to 129 mm Hg, HRs for incident CKD G3-G5 for the<110, 110 to 119, 130 to 139, and≥140 mm Hg categories were 0.84 (95% CI, 0.82-0.85), 0.92 (95% CI, 0.91-0.94), 1.11 (95% CI, 1.09-1.12), and 1.30 (95% CI, 1.28-1.31), respectively. For time-updated SBPs, corresponding HRs were 0.57 (95% CI, 0.56-0.59), 0.79 (95% CI, 0.78-0.80), 1.58 (95% CI, 1.55-1.60), and 2.49 (95% CI, 2.45-2.53), respectively. Treated as a continuous exposure, each 10-mm Hg higher SBP was associated with 35% higher risk for incident CKD G3-G5 (95% CI, 1.35-1.36). LIMITATIONS: Use of International Classification of Diseases codes to assess comorbid condition burden; residual confounding, and potential selection bias cannot be excluded. CONCLUSIONS: In this large national cohort study, higher SBPs were associated with higher risk for incident CKD G3-G5. These findings support evaluation of SBP-lowering strategies to reduce the development of CKD.

A Diet Rich in Vegetables and Fruit and Incident CKD: A Community-Based Prospective Cohort Study.

RATIONALE & OBJECTIVE: A diet rich in vegetables and fruit can lower blood pressure and may reduce cardiovascular risk. However, the association between this dietary pattern and incident chronic kidney disease in the general population is unknown. STUDY DESIGN: A community-based prospective cohort study. SETTING & PARTICIPANTS: 9,229 study participants with normal kidney function from the Korean Genome and Epidemiology Study database. PREDICTORS: Daily consumption of nonfermented and fermented vegetables and fruit classified into tertiles based on a validated semiquantitative food-frequency questionnaire. OUTCOMES: Incident occurrence of estimated glomerular filtration rate (eGFR) < 60mL/min/1.73m2, incident proteinuria (≥1+ by dipstick test), and repeated measures of estimated net endogenous acid production. ANALYTICAL APPROACH: Multivariable cause-specific hazards model to assess the association of vegetable and fruit intake with incident chronic kidney disease. RESULTS: During a mean follow-up of 8.2 years, 1,741 (21.9/1,000 person-years [PY]) participants developed eGFRs < 60mL/min/1.73m2. Incident eGFR < 60mL/min/1.73m2 occurred less frequently with higher intake of nonfermented vegetables, occurring at rates of 22.8/1,000 PY, 22.7/1,000 PY, and 20.1/1,000 PY for the lowest, middle, and highest tertiles, respectively; P for trend < 0.001. The incidence of proteinuria was also lower in the middle and highest tertiles. In a multivariable cause-specific hazards model, the highest tertile of nonfermented vegetable intake was associated with 14% lower risk for incident eGFR < 60mL/min/1.73m2 than the lowest tertile. The highest tertile was also associated with 32% lower risk for proteinuria than the lowest tertile. There were no associations of fermented vegetable and fruit intake with incidence of eGFR < 60mL/min/1.73m2. However, the highest tertiles of both fermented vegetable and fruit intake were associated with 14% and 45% lower risks for incident proteinuria compared with the lowest tertiles (both P < 0.001). During follow-up, estimated net endogenous acid production increased in the lowest tertile of intake of nonfermented or fermented vegetables and fruit, whereas it decreased in the highest tertile. LIMITATIONS: Self-reported dietary intake, single ethnicity population. CONCLUSIONS: A diet rich in vegetables and fruit may reduce the risk for kidney disease.

Coffee Consumption and Incident Kidney Disease: Results From the Atherosclerosis Risk in Communities (ARIC) Study.

BACKGROUND: Moderate coffee consumption has been suggested to be associated with lower risk for chronic conditions such as diabetes, a major precursor to chronic kidney disease (CKD). However, the association between coffee and CKD has not been fully established. STUDY DESIGN: Prospective cohort study. SETTING & PARTICIPANTS: 14,209 participants aged 45 to 64 years from the Atherosclerosis Risk in Communities (ARIC) Study. PREDICTORS: Coffee consumption (cups per day) was assessed at visits 1 (1987-1989) and 3 (1993-1995) using food frequency questionnaires. OUTCOMES: Incident CKD defined as estimated glomerular filtration rate < 60mL/min/1.73m2 accompanied by ≥25% estimated glomerular filtration rate decline, CKD-related hospitalization or death, or end-stage renal disease. RESULTS: There were 3,845 cases of incident CKD over a median of 24 years of follow-up. Men, whites, current smokers, and participants without comorbid conditions were more likely to consume higher amounts of coffee per day. After adjustment for demographic, clinical, and dietary factors, higher categories of coffee consumption were associated with lower risk for incident CKD compared with those who never consumed coffee (HR for <1 cup per day, 0.90 [95% CI, 0.82-0.99]; 1-<2 cups per day, 0.90 [95% CI, 0.82-0.99]; 2-<3 cups per day, 0.87 [95% CI, 0.77-0.97]; and ≥3 cups per day, 0.84 [95% CI, 0.75-0.94]). In continuous analysis, for each additional cup of coffee consumed per day, risk for incident CKD was lower by 3% (HR, 0.97; 95% CI, 0.95-0.99; P<0.001). LIMITATIONS: Self-reported coffee consumption and observational design. CONCLUSIONS: Participants who drank higher amounts of coffee had lower risk for incident CKD after adjusting for covariates. Coffee consumers may not be at adverse risk for kidney disease.

Validity of a Risk Prediction Equation for CKD After 10 Years of Follow-up in a Japanese Population: The Ibaraki Prefectural Health Study.

BACKGROUND: Chronic kidney disease (CKD) is an important health problem for which risk equations have been developed for Western populations. This study aimed to develop and validate a risk prediction equation for CKD in a Japanese population. STUDY DESIGN: Observational cohort study. SETTING & PARTICIPANTS: The study included 135,007 participants who completed an annual health checkup in 1993 to 1996 in the Ibaraki Prefecture in Japan. Participants were initially free of CKD (defined as stage 3, 4, or 5 CKD or proteinuria [2+ or 3+] by dipstick). Follow-up information was available from health checkups 10 years after the initial evaluation. We used data from 40,963 women and 17,892 men in the northern region of the prefecture for the development of risk prediction equations and 53,042 women and 23,110 men in the southern region for external validation. PREDICTORS: Age, estimated glomerular filtration rate (eGFR), body mass index, proteinuria, hematuria, hypertension, diabetes mellitus, smoking, and drinking. OUTCOME: Occurrence of CKD (defined as eGFR<60mL/min/1.73m2 and/or proteinuria [2+ or 3+] by dipstick). ANALYTICAL APPROACH: Logistic regression analysis to estimate risk for CKD stratified by sex. RESULTS: During follow-up, 7,500 cases of CKD developed in the northern region and 8,964, in the southern region. Older age, proteinuria (1+), higher systolic blood pressure, medication for hypertension, and current smoking were associated with increased risk for CKD in both sexes, whereas higher eGFR and daily alcohol intake were associated with lower risk. C statistics of risk estimation equations for CKD at 10 years were >0.8 for both the development and external validation populations, and discrimination of the risk estimation was fairly good in women and men. LIMITATIONS: Fluctuations in variables were not evaluated because the study used annual health checkups. This study excluded a large number of people for whom a 10-year health checkup was not available. CONCLUSIONS: Estimations of risk for CKD after 10 years of follow-up in a general Japanese population can be achieved with a high level of validity.

Association Between Gestational Diabetes and Incident Maternal CKD: The Coronary Artery Risk Development in Young Adults (CARDIA) Study.

BACKGROUND: Gestational diabetes mellitus (GDM) is associated with increased risk for diabetes mellitus, metabolic syndrome, and cardiovascular disease. We evaluated whether GDM is associated with incident chronic kidney disease (CKD), controlling for prepregnancy risk factors for both conditions. STUDY DESIGN: Prospective cohort. SETTING & PARTICIPANTS: Of 2,747 women (aged 18-30 years) enrolled in the Coronary Artery Risk Development in Young Adults (CARDIA) Study in 1985 to 86, we studied 820 who were nulliparous at enrollment, delivered at least 1 pregnancy longer than 20 weeks' gestation, and had kidney function measurements during 25 years of follow-up. PREDICTOR: GDM was self-reported by women for each pregnancy. OUTCOMES: CKD was defined as the development of estimated glomerular filtration rate (eGFR)<60mL/min/1.73m2 or urine albumin-creatinine ratio ≥ 25mg/g at any one CARDIA examination in years 10, 15, 20, or 25. MEASUREMENTS: HRs for developing CKD were estimated for women who developed GDM versus women without GDM using complementary log-log models, adjusting for prepregnancy age, systolic blood pressure, dyslipidemia, body mass index, smoking, education, eGFR, fasting glucose concentration, physical activity level (all measured at the CARDIA examination before the first pregnancy), race, and family history of diabetes. We explored for an interaction between race and GDM. RESULTS: During a mean follow-up of 20.8 years, 105 of 820 (12.8%) women developed CKD, predominantly increased urine albumin excretion (98 albuminuria only, 4 decreased eGFR only, and 3 both). There was evidence of a GDM-race interaction on CKD risk (P=0.06). Among black women, the adjusted HR for CKD was 1.96 (95% CI, 1.04-3.67) in GDM compared with those without GDM. Among white women, the HR was 0.65 (95% CI, 0.23-1.83). LIMITATIONS: Albuminuria was assessed by single untimed measurements of urine albumin and creatinine. CONCLUSIONS: GDM is associated with the subsequent development of albuminuria among black women in CARDIA.

Blood Lead Levels and Decreased Kidney Function in a Population-Based Cohort.

BACKGROUND: Environmental lead exposure has been associated with decreased kidney function, but evidence from large prospective cohort studies examining low exposure levels is scarce. We assessed the association of low levels of lead exposure with kidney function and kidney disease. STUDY DESIGN: Prospective population-based cohort. SETTING & PARTICIPANTS: 4,341 individuals aged 46 to 67 years enrolled into the Malmö Diet and Cancer Study-Cardiovascular Cohort (1991-1994) and 2,567 individuals subsequently followed up (2007-2012). PREDICTOR: Blood lead concentrations in quartiles (Q1-Q4) at baseline. OUTCOMES: Change in estimated glomerular filtration rate (eGFR) between the baseline and follow-up visit based on serum creatinine level alone or in combination with cystatin C level. Chronic kidney disease (CKD) incidence (185 cases) through 2013 detected using a national registry. MEASUREMENTS: Multivariable-adjusted linear regression models to assess associations between lead levels and eGFRs at baseline and follow-up and change in eGFRs over time. Cox regression was used to examine associations between lead levels and CKD incidence. Validation of 100 randomly selected CKD cases showed very good agreement between registry data and medical records and laboratory data. RESULTS: At baseline, 60% of study participants were women, mean age was 57 years, and median lead level was 25 (range, 1.5-258) µg/L. After a mean of 16 years of follow-up, eGFR decreased on average by 6mL/min/1.73m2 (based on creatinine) and 24mL/min/1.73m2 (based on a combined creatinine and cystatin C equation). eGFR change was higher in Q3 and Q4 of blood lead levels compared with Q1 (P for trend = 0.001). The HR for incident CKD in Q4 was 1.49 (95% CI, 1.07-2.08) compared with Q1 to Q3 combined. LIMITATIONS: Lead level measured only at baseline, moderate number of CKD cases, potential unmeasured confounding. CONCLUSIONS: Low-level lead exposure was associated with decreased kidney function and incident CKD. Our findings suggest lead nephrotoxicity even at low levels of exposure.

Dietary total antioxidant capacity and incidence of chronic kidney disease in subjects with dysglycemia: Tehran Lipid and Glucose Study.

PURPOSE: We aimed to investigate the association of dietary total antioxidant capacity (TAC) with incidence of CKD in subjects with dysglycemia. METHODS: We followed-up 1179 subjects aged ≥30 years with dysglycemia from the Tehran Lipid and Glucose Study (TLGS) for 3 years, who were initially free of CKD. Dietary intakes of TAC, vitamin C, vitamin E, and ß-carotene were assessed by a food-frequency questionnaire at the baseline. Dietary TAC was estimated using the oxygen radical absorbance capacity method. Estimated glomerular filtration rate (eGFR) was calculated, using the Modification of Diet in Renal Disease Study equation and CKD was defined as eGFR <60 mL/min/1.73 m2. Odds ratios (ORs) using multivariable logistic regression were reported for the association of incident CKD with dietary TAC. RESULTS: A total of 197 (16.7%) cases of incident CKD were recorded after 3 years of follow-up. After adjustment for age, sex, smoking, physical activity, body mass index, hypertension, and total energy intake, the top tertile of dietary TAC compared to the bottom was associated with 39% [95% confidence interval (CI) = 0.40-0.93] lower risk of incident CKD (P for trend = 0.025). Furthermore, the highest tertile of vitamin C intake compared to the lowest risk of incident CKD was decreased (OR 0.60; 95% CI 0.38-0.93, P trend 0.023). Intakes of vitamin E and ß-carotene were not significantly associated with incident CKD risk. CONCLUSION: Our findings suggest that diets high in TAC are associated with a lower risk of incident CKD among subjects with hyperglycemia after 3 years of follow-up.

Association of Increasing GFR with Change in Albuminuria in the General Population.

BACKGROUND AND OBJECTIVES: Hyperfiltration at the single-nephron level has been proposed as an early stage of kidney dysfunction of different origins. Evidence supporting this hypothesis in humans is lacking, because there is no method of measuring single-nephron GFR in humans. However, increased whole-kidney GFR in the same individual implies an increased single-nephron GFR, because the number of nephrons does not increase with age. We hypothesized that an increase in GFR would be associated with an increased albumin-to-creatinine ratio in a cohort of the general population. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We measured GFR by iohexol clearance at baseline in 2007-2009 and follow-up after 5.6 years in a representative sample of 1246 persons (aged 50-62 years) who were nondiabetic from the general population of Tromso, northern Norway. Participants were without cardiovascular disease, kidney disease, or diabetes at baseline. We investigated the association between change in GFR and change in albumin-to-creatinine ratio. Increased GFR was defined as a positive change in GFR (change in GFR>0 ml/min) from baseline to follow-up. An albumin-to-creatinine ratio >30 mg/g was classified as albuminuria. RESULTS: Change in GFR was positively associated with a change in albumin-to-creatinine ratio in the entire cohort in the multiple linear regression. The albumin-to-creatinine ratiofollow-up-to-albumin-to-creatinine ratiobaseline ratio increased by 8.0% (95% confidence interval, 1.4 to 15.0) per SD increase in change in GFR. When participants with increased GFR (n=343) were compared with those with a reduced GFR (n=903), the ratio increased by 16.3% (95% confidence interval, 1.1 to 33.7). The multivariable adjusted odds ratio for incident albuminuria (n=14) was 4.98 (95% confidence interval, 1.49 to 16.13) for those with an increased GFR (yes/no). CONCLUSIONS: Increasing GFR is associated with an increase in albumin-to-creatinine ratio and incident albuminuria in the general nondiabetic population. These findings support single-nephron hyperfiltration as a risk factor for albuminuria in the general population.