A systematic review of ambient heat and sleep in a warming climate.

Climate change is elevating nighttime and daytime temperatures worldwide, affecting a broad continuum of behavioral and health outcomes. Disturbed sleep is a plausible pathway linking rising ambient temperatures with several observed adverse human responses shown to increase during hot weather. This systematic review aims to provide a comprehensive overview of the literature investigating the relationship between ambient temperature and valid sleep outcomes measured in real-world settings, globally. We show that higher outdoor or indoor temperatures are generally associated with degraded sleep quality and quantity worldwide. The negative effect of heat persists across sleep measures, and is stronger during the hottest months and days, in vulnerable populations, and the warmest regions. Although we identify opportunities to strengthen the state of the science, limited evidence of fast sleep adaptation to heat suggests rising temperatures induced by climate change and urbanization pose a planetary threat to human sleep, and therefore health, performance, and wellbeing.

Metabolic Features of Increased Gut Permeability, Inflammation, and Altered Energy Metabolism Distinguish Agricultural Workers at Risk for Mesoamerican Nephropathy.

Mesoamerican nephropathy (MeN) is a form of chronic kidney disease found predominantly in young men in Mesoamerica. Strenuous agricultural labor is a consistent risk factor for MeN, but the pathophysiologic mechanism leading to disease is poorly understood. We compared the urine metabolome among men in Nicaragua engaged in sugarcane harvest and seed cutting (n = 117), a group at high risk for MeN, against three referents: Nicaraguans working less strenuous jobs at the same sugarcane plantations (n = 78); Nicaraguans performing non-agricultural work (n = 102); and agricultural workers in Spain (n = 78). Using proton nuclear magnetic resonance, we identified 136 metabolites among participants. Our non-hypothesis-based approach identified distinguishing urine metabolic features in the high-risk group, revealing increased levels of hippurate and other gut-derived metabolites and decreased metabolites related to central energy metabolism when compared to referent groups. Our complementary hypothesis-based approach, focused on nicotinamide adenine dinucleotide (NAD+) related metabolites, and revealed a higher kynurenate/tryptophan ratio in the high-risk group (p = 0.001), consistent with a heightened inflammatory state. Workers in high-risk occupations are distinguishable by urinary metabolic features that suggest increased gut permeability, inflammation, and altered energy metabolism. Further study is needed to explore the pathophysiologic implications of these findings.

Associations of wrong surgery with other critical healthcare quality and patient safety challenges: a cross-sectional nationwide study of 100 general hospitals in Spain.

Wrong surgery (wrong-site, wrong-procedure, or wrong-patient surgery) is among the most feared patient safety problems in hospitals. We aimed to evaluate associations between numeric assessment of risk assigned to wrong surgery with that of other healthcare quality and patient safety challenges. This nationwide study collected information from healthcare quality experts in charge of a clinical quality and/or patient safety department in general hospitals of ≥ 150 beds in Spain. Out of the 100 included hospitals, the highest strength of associations were observed with risk priority number (RPN) for hospital-acquired pressure ulcers, RPN for venous thromboembolism in hospitalized patients, RPN for incorrect patient identification, RPN for lack of informed consent for diagnostic or therapeutic procedures, RPN for catheter-related bacteremia, and RPN for adverse events and injuries due to medical devices related to use and/or design. These results are of potential interest for designing combined and coordinated strategies to improve patient safety in hospitals.

Responding to the need of postgraduate education for Planetary Health: Development of an online Master's Degree.

Planetary Health has emerged as a new approach to respond to the existential risks that the clime and global environmental crises pose to human societies. As stated by various stakeholders, the challenges involved in Planetary Health are of such magnitude that education must be at the forefront to obtain a meaningful response. Universities and higher education institutions have been specifically called to embed the concept of planetary stewardship in all curricula and train the next generation of researchers and change makers as a matter of urgency. As a response to this call, the Universitat Oberta de Catalunya (UOC), the Universitat Pompeu Fabra (UPF), and the Barcelona Institute for Global Health (ISGlobal) developed the first online and asynchronous Master in Science (MSc) in Planetary Health. The aim of the programme is to train a new generation of academics and professionals who understand the challenges of Planetary Health and have tools to tackle them. This article describes the development of the curriculum of this MSc, presents the main characteristics of the programme and discusses some of the challenges encountered in the development of the programme and its implementation. The design of this MSc was based on: the alignment of the programme with the principles for Planetary Health education with a focus on human health; a multi-, inter-, and trans-disciplinary approach; the urgency to respond to the Anthropocene challenges; and the commitment to the 2030 Agenda. The MSc was recognized as an official degree by the Agency for Quality of the Catalan University System, included in the European Quality Assurance Register for Higher Education, and the Spanish National Academic Coordination body in April 2021 and launched in October 2021. There are currently more than 50 students enrolled in the program coming from a broad range of disciplines and geographic locations. The information presented in this article and the discussion on challenges encountered in developing and implementing the programme can be useful for those working in the development of similar programs.

Air pollution and green spaces in relation to breast cancer risk among pre and postmenopausal women: A mega cohort from Catalonia.

BACKGROUND: The association between air pollution and green spaces with breast cancer risk stratified by menopausal status has not been frequently investigated despite its importance given the different impact of risk factors on breast cancer risk depending on menopausal status. OBJECTIVES: To study the association between air pollution, green spaces and pre and postmenopausal breast cancer risk. METHODS: We conducted a population-based cohort study using electronic primary care records in Catalonia. We included women aged 17-85 years free of cancer at study entry between 2009 and 2017. Our exposures were particulate matter <2.5 µm (PM2.5) & <10 µm (PM10), nitrogen dioxide (NO2), normalized difference vegetation index (NDVI), and percentage of green spaces estimated at the census tract level. Breast cancer was identified with ICD-10 code C50. We estimated cause-specific hazard ratios (HR) for the relationship between each individual exposure and pre and postmenopausal breast cancer risk, using linear and non-linear models. RESULTS: Of the 1,054,180 pre and 744,658 postmenopausal women followed for a median of 10 years, 6,126 and 17,858 developed breast cancer, respectively. Among premenopausal women, only very high levels of PM10 (≥46 µg/m3) were associated with increased cancer risk (compared to lower levels) in non-linear models. Among postmenopausal women, an interquartile range increase in PM2.5 (HR:1.03; 95%CI:1.01-1.04), PM10 (1.03; 1.01-1.05), and NO2 (1.05; 1.02-1.08) were associated with higher cancer risk. NDVI was negatively associated with decreased cancer risk only among postmenopausal women who did not change residence during follow-up (0.84; 0.71-0.99) or who were followed for at least three years (0.82; 0.69-0.98). DISCUSSION: Living in areas with high concentrations of PM2.5, PM10, and NO2 increases breast cancer risk in postmenopausal women while long-term exposure to green spaces may decrease this risk. Only very high concentrations of PM10 increase breast cancer risk in premenopausal women.

Auditory hindsight bias in school-age children.

We report two experiments investigating hindsight bias in children, focusing on a rarely studied age range of 8-13 years. In Experiment 1, we asked children to complete both an auditory hindsight task and a visual hindsight task. Children exhibited hindsight bias in both tasks, and the bias decreased with age. In Experiment 2, we further explored children 's auditory hindsight bias by contrasting performance in hypothetical and memory designs (which previous research with adults had found to involve different mechanisms-fluency vs. memory reconstruction). Children exhibited auditory hindsight bias in both tasks, but only in the hypothetical design was the bias magnitude modulated by a priming manipulation designed to increase fluency, replicating and extending the pattern found in adults to children.

Ambient Air Pollution in Relation to SARS-CoV-2 Infection, Antibody Response, and COVID-19 Disease: A Cohort Study in Catalonia, Spain (COVICAT Study).

BACKGROUND: Emerging evidence links ambient air pollution with coronavirus 2019 (COVID-19) disease, an association that is methodologically challenging to investigate. OBJECTIVES: We examined the association between long-term exposure to air pollution with SARS-CoV-2 infection measured through antibody response, level of antibody response among those infected, and COVID-19 disease. METHODS: We contacted 9,605 adult participants from a population-based cohort study in Catalonia between June and November 2020; most participants were between 40 and 65 years of age. We drew blood samples from 4,103 participants and measured immunoglobulin M (IgM), IgA, and IgG antibodies against five viral target antigens to establish infection to the virus and levels of antibody response among those infected. We defined COVID-19 disease using self-reported hospital admission, prior positive diagnostic test, or more than three self-reported COVID-19 symptoms after contact with a COVID-19 case. We estimated prepandemic (2018-2019) exposure to fine particulate matter [PM with an aerodynamic diameter of ≤2.5µm (PM2.5)], nitrogen dioxide (NO2), black carbon (BC), and ozone (O3) at the residential address using hybrid land-use regression models. We calculated log-binomial risk ratios (RRs), adjusting for individual- and area-level covariates. RESULTS: Among those tested for SARS-CoV-2 antibodies, 743 (18.1%) were seropositive. Air pollution levels were not statistically significantly associated with SARS-CoV-2 infection: Adjusted RRs per interquartile range were 1.07 (95% CI: 0.97, 1.18) for NO2, 1.04 (95% CI: 0.94, 1.14) for PM2.5, 1.00 (95% CI: 0.92, 1.09) for BC, and 0.97 (95% CI: 0.89, 1.06) for O3. Among infected participants, exposure to NO2 and PM2.5 were positively associated with IgG levels for all viral target antigens. Among all participants, 481 (5.0%) had COVID-19 disease. Air pollution levels were associated with COVID-19 disease: adjusted RRs=1.14 (95% CI: 1.00, 1.29) for NO2 and 1.17 (95% CI: 1.03, 1.32) for PM2.5. Exposure to O3 was associated with a slightly decreased risk (RR=0.92; 95% CI: 0.83, 1.03). Associations of air pollution with COVID-19 disease were more pronounced for severe COVID-19, with RRs=1.26 (95% CI: 0.89, 1.79) for NO2 and 1.51 (95% CI: 1.06, 2.16) for PM2.5. DISCUSSION: Exposure to air pollution was associated with a higher risk of COVID-19 disease and level of antibody response among infected but not with SARS-CoV-2 infection. https://doi.org/10.1289/EHP9726.

Infection induced SARS-CoV-2 seroprevalence and heterogeneity of antibody responses in a general population cohort study in Catalonia Spain.

Sparse data exist on the complex natural immunity to SARS-CoV-2 at the population level. We applied a well-validated multiplex serology test in 5000 participants of a general population study in Catalonia in blood samples collected from end June to mid November 2020. Based on responses to fifteen isotype-antigen combinations, we detected a seroprevalence of 18.1% in adults (n = 4740), and modeled extrapolation to the general population of Catalonia indicated a 15.3% seroprevalence. Antibodies persisted up to 9 months after infection. Immune profiling of infected individuals revealed that with increasing severity of infection (asymptomatic, 1-3 symptoms, ≥ 4 symptoms, admitted to hospital/ICU), seroresponses were more robust and rich with a shift towards IgG over IgA and anti-spike over anti-nucleocapsid responses. Among seropositive participants, lower antibody levels were observed for those ≥ 60 years vs < 60 years old and smokers vs non-smokers. Overweight/obese participants vs normal weight had higher antibody levels. Adolescents (13-15 years old) (n = 260) showed a seroprevalence of 11.5%, were less likely to be tested seropositive compared to their parents and had dominant anti-spike rather than anti-nucleocapsid IgG responses. Our study provides an unbiased estimate of SARS-CoV-2 seroprevalence in Catalonia and new evidence on the durability and heterogeneity of post-infection immunity.

Climate Trends at a Hotspot of Chronic Kidney Disease of Unknown Causes in Nicaragua, 1973-2014.

An ongoing epidemic of chronic kidney disease of uncertain etiology (CKDu) afflicts large parts of Central America and is hypothesized to be linked to heat stress at work. Mortality rates from CKDu appear to have increased dramatically since the 1970s. To explore this relationship, we assessed trends in maximum and minimum temperatures during harvest months between 1973 and 2014 as well as in the number of days during the harvest season for which the maximum temperature surpassed 35 °C. Data were collected at a weather station at a Nicaraguan sugar company where large numbers of workers have been affected by CKDu. Monthly averages of the daily maximum temperatures between 1996 and 2014 were also compared to concurrent weather data from eight Automated Surface Observing System Network weather stations across Nicaragua. Our objectives were to assess changes in temperature across harvest seasons, estimate the number of days that workers were at risk of heat-related illness and compare daily maximum temperatures across various sites in Nicaragua. The monthly average daily maximum temperature during the harvest season increased by 0.7 °C per decade between 1973 and 1990. The number of days per harvest season with a maximum temperature over 35 °C increased by approximately five days per year between 1974 and 1990, from 32 days to 114 days. Between 1991 and 2013, the number of harvest days with a maximum temperature over 35 °C decreased by two days per year, and the monthly average daily maximum temperature decreased by 0.3 °C per decade. Comparisons with weather stations across Nicaragua demonstrate that this company is located in one of the consistently hottest regions of the country.

Blood lead levels in indigenous peoples living close to oil extraction areas in the Peruvian Amazon.

BACKGROUND: High blood lead levels (BLLs) have been previously reported in indigenous people living in communities in the northern Peruvian Amazon. Oil extraction activities have been conducted in the area since the 1970s and have been identified as a source of lead exposure. OBJECTIVE: Measure BLL and assess risk factors associated with BLL among indigenous populations from four river basins of the northern Peruvian Amazon. METHODS: Participants from 39 communities were selected using a two-stage stratified random selection strategy and were visited between May and June 2016. Information on risk factors was collected using structured questionnaires and blood samples were taken. Overall, complete information was available from 1047 individuals (309 < 12 years old, 738 ≥ 12 years). BLL was determined using atomic absorption spectrophotometry in a graphite chamber. Weighted linear logistic regression models were used to study the association between socio-demographic variables, self-reported life-style factors, environmental, geographical and occupational exposures and BLLs. RESULTS: Geometric mean (95% CI) BLL was 4.9 (4.5, 5.4) µg/dL in participants <12 years and 5.7 (5.4, 6.0) µg/dL in older participants. There were marked differences in BLL between river basins with the highest levels observed in the Corrientes river basin [8.1 (7.2, 9.1) µg/dL <12 years and 8.8 (8.0, 9.6) µg/dL older participants]. High BLL was associated with older age, being male, living in the Pastaza, Tigre or Corrientes river basins and consumption of fish offal in children and adults. Increased Euclidean distance between residence and oil production facilities was associated with a small reduction in BLL. CONCLUSION: BLLs that pose a health risk were detected in the study population of a non-industrialized and remote area of the Amazon. The highest BLLs were observed in those river basins where relative oil extraction activity and environmental levels of contaminants have been reported to be greatest.

Root causes of adverse drug events in hospitals and artificial intelligence capabilities for prevention.

AIMS: To identify and prioritize the root causes of adverse drug events (ADEs) in hospitals and to assess the ability of artificial intelligence (AI) capabilities to prevent ADEs. DESIGN: A mixed method design was used. METHODS: A cross-sectional study for hospitals in Spain was carried out between February and April 2019 to identify and prioritize the root causes of ADEs. A nominal group technique was also used to assess the ability of AI capabilities to prevent ADEs. RESULTS: The main root cause of ADEs was a lack of adherence to safety protocols (64.8%), followed by identification errors (57.4%), and fragile and polymedicated patients (44.4%). An analysis of the AI capabilities to prevent the root causes of ADEs showed that identification and reading are two potentially useful capabilities. CONCLUSION: Identification error is one of the main root causes of drug adverse events and AI capabilities could potentially prevent drug adverse events. IMPACT: This study highlights the role of AI capabilities in safely identifying both patients and drugs, which is a crucial part of the medication administration process, and how this can prevent ADEs in hospitals.

Ranking Quality and Patient Safety Challenges: A Nationwide Survey of Healthcare Quality Experts From General Hospitals in Spain.

OBJECTIVE: The aim of the study was to identify and rank leading healthcare quality and patient safety challenges of general hospitals in Spain. METHODS: A novel online cross-sectional survey for hospitals with 150 or more beds carried out between June and September 2018. Sample frame is hospitals of the National Catalogue of Hospitals of the Ministry of Health in Spain (N = 888). Eligibility criteria are quality experts of clinical quality and/or patient safety services of general hospitals with 150 or more beds. Challenges were ranked using a risk priority number (RPN) calculated from the product of severity, frequency, and detectability scores. RESULTS: Targeted hospitals were 234. The contact rate was 97.4%, representing 63% of total beds nationwide. One hundred hospitals completed the questionnaire. According to the RPN, the top five challenges were incorrect hand hygiene of health professionals (mean RPN = 334.5, SD = 198.5), ineffective interprofessional communication (mean RPN = 334.3, SD = 169.5), medication errors in transitions of care (mean RPN = 254.0, SD = 151.0), low reporting rates of patient safety incidents and adverse events (mean RPN = 252.3, SD = 176.3), and antimicrobial resistance due to inappropriate use of antibiotics (mean RPN = 243.5, SD = 158.7). CONCLUSIONS: This pioneer study of ranking quality and patient safety challenges of hospitals in Spain provides an evidence-based and context-specific foundation for quality improvement decision-making.

Residential proximity to industrial pollution sources and colorectal cancer risk: A multicase-control study (MCC-Spain).

BACKGROUND: Colorectal cancer is the third most frequent tumor in males and the second in females worldwide. In Spain, it is an important and growing health problem, and epidemiologic research focused on potential risk factors, such as environmental exposures, is necessary. OBJECTIVES: To analyze the association between colorectal cancer risk and residential proximity to industries, according to pollution discharge route, industrial groups, categories of carcinogens and other toxic substances, and specific pollutants released, in the context of a population-based multicase-control study of incident cancer carried out in Spain (MCC-Spain). METHODS: MCC-Spain included 557 colorectal cancer cases and 2948 controls in 11 provinces, frequency matched by sex, age, and region of residence. Distances were computed from subjects' residences to each of the 134 industries located in the study area. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (95%CIs) for categories of distance (from 1 km to 3 km) to industrial facilities, adjusting for matching variables and other confounders. RESULTS: Excess risk (OR; 95%CI) of colorectal cancer was detected near industries overall for all distances analyzed, from 1 km (2.03; 1.44-2.87) to 3 km (1.26; 1.00-1.59). In general, industries releasing pollutants to air showed higher excess risks than facilities releasing pollution to water. By industrial sector, excess risk (OR; 95%CI) was found near (≤3 km) production of metals (2.66; 1.77-4.00), surface treatment of metals (1.48; 1.08-2.02), glass and mineral fibers (2.06; 1.39-3.07), organic chemical industry (4.80; 3.20-7.20), inorganic chemical industry (6.74; 4.38-10.36), food/beverage sector (3.34; 2.38-4.68), and surface treatment using organic solvents (6.16; 4.06-9.36). By pollutants, the main excess risks (OR; 95%CI) were found near (≤3 km) industries releasing nonylphenol (9.19; 5.91-14.28), antimony (5.30; 3.45-8.15), naphthalene (3.11; 2.16-4.49), organotin compounds (2.64; 1.76-3.98), manganese (2.53; 1.63-3.93), dichloromethane (2.52; 1.74-3.66), and vanadium (2.49; 1.59-3.91). CONCLUSIONS: Our results support the hypothesis that residing in the proximity of industries may be a risk factor for colorectal cancer.

Validation of self-reported perception of proximity to industrial facilities: MCC-Spain study.

BACKGROUND: Self-reported data about environmental exposures can lead to measurement error. OBJECTIVES: To validate the self-reported perception of proximity to industrial facilities. METHODS: MCC-Spain is a population-based multicase-control study of cancer in Spain that recruited incident cases of breast, colorectal, prostate, and stomach cancer. The participant's current residence and the location of the industries were geocoded, and the linear distance between them was calculated (gold standard). The epidemiological questionnaire included a question to determine whether the participants perceived the presence of any industry at ≤1 km from their residences. Sensitivity and specificity of individuals' perception of proximity to industries were estimated as measures of classification accuracy, and the area under the curve (AUC) and adjusted odds ratios (aORs) of misclassification were calculated as measures of discrimination. Analyses were performed for all cases and controls, and by tumor location, educational level, sex, industrial sector, and length of residence. Finally, aORs of cancer associated with real and self-reported distances were calculated to explore differences in the estimation of risk between these measures. RESULTS: Sensitivity of the questionnaire was limited (0.48) whereas specificity was excellent (0.89). AUC was sufficient (0.68). Participants with breast (aOR(95%CI) = 2.03 (1.67;2.46)), colorectal (aOR(95%CI) = 1.41 (1.20;1.64)) and stomach (aOR(95%CI) = 1.59 (1.20;2.10)) cancer showed higher risk of misclassification than controls. This risk was higher for lower educational levels (aOR15 years (95%CI) = 0.56 (0.36;0.85)). The use of self-reported proximity vs. real distance to industrial facilities biased the effect on cancer risk towards the nullity. CONCLUSIONS: Self-reported distance to industrial facilities can be a useful tool for hypothesis generation, but hypothesis-testing studies should use real distance to report valid conclusions. The sensitivity of the question might be improved with a more specific formulation.

Green spaces, excess weight and obesity in Spain.

BACKGROUND: The epidemiological evidence on green spaces and obesity is inconsistent. OBJECTIVES: To study the association of access to green spaces and surrounding greenness with obesity in Spain. METHODS: We enrolled 2354 individuals 20-85 years from urban areas of seven provinces of Spain between 2008-13. Subjects were randomly selected population controls of the MCC-Spain case-control study. We geocoded current residences and defined exposures in a buffer of 300 m around them: i) access to green space, identified using Urban Atlas, and ii) levels of surrounding greenness, measured by the Normalized Difference Vegetation Index. We examined excess weight/obesity as binary outcomes based on body mass index and waist-hip ratio. We examined effect modification by genetic factors, sex and individual socio-economic status and mediation by physical activity and concentrations of PM2.5 and NO2. To assess potential effect modification by genetic factors, we used a polygenic risk score based on obesity polymorphisms detected in genome-wide association studies. We used logistic mixed-effects models with a random effect for catchment area adjusted for potential confounders. RESULTS: Access to green space was associated with a reduced risk of excess weight/obesity after adjusting for confounders [excess weight: OR (95%CI) = 0.82 (0.63, 1.07), p-value = 0.143; abdominal obesity: OR (95%CI) = 0.68 (0.45, 1.01), p-value = 0.057]. In the stratified analysis, this association was only observed in women. Associations between surrounding greenness and excess weight/obesity were null or modest based on a 1 IQR increase in NDVI [excess weight: OR (95%CI) = 0.99 (0.88, 1.11), p-value = 0.875; abdominal obesity: OR (95%CI) = 0.91 (0.79, 1.05), p-value = 0.186]. The observed associations were not mediated by physical activity or air pollution. DISCUSSION: Access to green space may be associated with decreased risk of excess weight/obesity among women in Spain. Mechanisms explaining this association remain unclear.

Rationale and population-based prospective cohort protocol for the disadvantaged populations at risk of decline in eGFR (CO-DEGREE).

INTRODUCTION: A recently recognised form of chronic kidney disease (CKD) of unknown origin (CKDu) is afflicting communities, mostly in rural areas in several regions of the world. Prevalence studies are being conducted in a number of countries, using a standardised protocol, to estimate the distribution of estimated glomerular filtration rate (eGFR), and thus identify communities with a high prevalence of reduced glomerular filtration rate (GFR). In this paper, we propose a standardised minimum protocol for cohort studies in high-risk communities aimed at investigating the incidence of, and risk factors for, early kidney dysfunction. METHODS AND ANALYSIS: This generic cohort protocol provides the information to establish a prospective population-based cohort study in low-income settings with a high prevalence of CKDu. This involves a baseline survey that included key elements from the DEGREE survey (eg, using the previously published DEGREE methodology) of a population-representative sample, and subsequent follow-up visits in young adults (without a pre-existing diagnosis of CKD (eGFR<60 mL/min/1.73m2), proteinuria or risk factors for CKD at baseline) over several years. Each visit involves a core questionnaire, and collection and storage of biological samples. Local capacity to measure serum creatinine will be required so that immediate feedback on kidney function can be provided to participants. After completion of follow-up, repeat measures of creatinine should be conducted in a central laboratory, using reference standards traceable to isotope dilution mass spectrometry (IDMS) quality control material to quantify the main outcome of eGFR decline over time, alongside a description of the early evolution of disease and risk factors for eGFR decline. ETHICS AND DISSEMINATION: Ethical approval will be obtained by local researchers, and participants will provide informed consent before the study commences. Participants will typically receive feedback and advice on their laboratory results, and referral to a local health system where appropriate.

Prevalence of and risk factors for chronic kidney disease of unknown aetiology in India: secondary data analysis of three population-based cross-sectional studies.

OBJECTIVES: To assess whether chronic kidney disease of unknown aetiology (CKDu) is present in India and to identify risk factors for it using population-based data and standardised methods. DESIGN: Secondary data analysis of three population-based cross-sectional studies conducted between 2010 and 2014. SETTING: Urban and rural areas of Northern India (states of Delhi and Haryana) and Southern India (states of Tamil Nadu and Andhra Pradesh). PARTICIPANTS: 12 500 individuals without diabetes, hypertension or heavy proteinuria. OUTCOME MEASURES: Mean estimated glomerular filtration rate (eGFR) and prevalence of eGFR below 60 mL/min per 1.73 m2 (eGFR <60) in individuals without diabetes, hypertension or heavy proteinuria (proxy definition of CKDu). RESULTS: The mean eGFR was 105.0±17.8 mL/min per 1.73 m2. The prevalence of eGFR <60 was 1.6% (95% CI=1.4 to 1.7), but this figure varied markedly between areas, being highest in rural areas of Southern Indian (4.8% (3.8 to 5.8)). In Northern India, older age was the only risk factor associated with lower mean eGFR and eGFR <60 (regression coefficient (95% CI)=-0.94 (0.97 to 0.91); OR (95% CI)=1.10 (1.08 to 1.11)). In Southern India, risk factors for lower mean eGFR and eGFR <60, respectively, were residence in a rural area (-7.78 (-8.69 to -6.86); 4.95 (2.61 to 9.39)), older age (-0.90 (-0.93 to -0.86); 1.06 (1.04 to 1.08)) and less education (-0.94 (-1.32 to -0.56); 0.67 (0.50 to 0.90) for each 5 years at school). CONCLUSIONS: CKDu is present in India and is not confined to Central America and Sri Lanka. Identified risk factors are consistent with risk factors previously reported for CKDu in Central America and Sri Lanka.