chronic kidney disease ( ckd ) is a major global health burden due to its high prevalence and associated risk of end - stage renal disease ( esrd ) , cardiovascular disease ( cvd ) , and premature death ( 13 ) . the global burden of disease study 2013 estimated 956,200 deaths worldwide were directly attributable to ckd in 2013 , which represents a 134.6% increase from 1990 ( 4 ) . in addition , ckd was ranked as the 19 highest cause of years of life lost in 2013 ( 4 ) . this number of deaths and years of life lost has almost certainly underestimated the disease burden of ckd , as it probably only captures deaths due to esrd . it is well documented that cvd causes most of the deaths in patients with ckd ( 2,3 ) . worldwide , an estimated 1.9 million esrd patients were on renal replacement therapy in 2010 ( 5 ) . medical costs for the treatment of ckd and esrd are enormous and represent an immense financial burden to families and society as a whole . for example , overall us medicare expenditures for ckd and renal replacement therapy in 2010 were 41.0 and 32.9 billion us dollars , respectively , accounting for 24% of the total medicare budget ( 6 ) . diabetes and hypertension are the leading causes of ckd in all high - income countries and many low- and middle - income countries ( 1 ) . the global epidemic of diabetes and hypertension could lead to a worldwide increase in prevalence and in the number of persons with ckd and its complications without effective interventions ( 7,8 ) . although the prevalence of ckd has been reported in individual countries , global estimates of ckd prevalence and absolute burden are not available . accurate estimates of the worldwide prevalence of this condition are essential as a source of primary information and for rational planning of health services . quantifying the global burden of ckd will allow public - health policy - makers around the world to assign sufficient priority and resources to its prevention and treatment . we aimed to estimate the global prevalence and absolute burden of ckd in 2010 by pooling data from population - based studies worldwide . a total of 35 reports from 33 studies conducted in 32 countries , which represent 48.6% of the global population 20 years old , were included in the analysis ( figure 1 ) ( 943 ) . among the included studies , 16 were conducted in nationally representative samples and the rest were in multisite or regional samples ( table 1 ) . the crude prevalence of ckd stages 15 varied from 4.5% in south korea to 25.7% in el salvador in men , and from 4.1% in saudi arabia to 16.0% in singapore in women ; stages 35 varied from 1.3% in china to 15.4% in nepal in men and from 1.7% in singapore to 21.3% in nepal in women . the age - standardized global prevalence of ckd stages 15 among adults aged 20 years in 2010 was 10.4% in men ( 95% ci 9.3 to 11.9% ) and 11.8% in women ( 11.2 to 12.6% ) . the age - standardized prevalence was 8.6% in men ( 7.3 to 9.8% ) and 9.6% in women ( 7.7 to 11.1% ) in high - income countries , and 10.6% in men ( 9.4 to 13.1% ) and 12.5% in women ( 11.8 to 14.0% ) in low- and middle - income countries ( table 2 ) . the age - standardized global prevalence of ckd stages 35 among adults aged 20 years in 2010 was 4.7% in men ( 95% ci 3.4 to 6.7% ) and 5.8% in women ( 4.4 to 8.1% ) . the age - standardized prevalence was 4.3% in men ( 3.5 to 5.2% ) and 5.7% in women ( 4.4 to 7.6% ) in high - income countries , and 4.6% in men ( 3.1 to 7.7% ) and 5.6% in women ( 3.9 to 9.2% ) in low- and middle - income countries . the estimated total number of adults with any stage of ckd in 2010 was 225.7 million ( 205.7 to 257.4 million ) men and 271.8 million ( 258.0 to 293.7 million ) women worldwide . the estimated total number of adults with any stage of ckd was 48.3 million ( 42.3 to 53.3 million ) men and 61.7 million ( 50.4 to 69.9 million ) women in high - income countries , and 177.4 million ( 162.9 to 209.0 million ) men and 210.1 million ( 200.8 to 231.7 million ) women in low- and middle - income countries ( table 2 ) . the estimated total number of adults with ckd stages 35 in 2010 was 100.6 million ( 72.0 to 146.4 million ) men and 135.8 million ( 102.7 to 193.9 million ) women worldwide . the estimated total number of adults with ckd stages 35 was 26.1 million ( 22.0 to 31.1 million ) men and 44.1 million ( 35.3 to 54.8 million ) women in high - income countries , and 74.5 million ( 50.3 to 123.5 million ) men and 91.7 million ( 66.7 to 143.1 million ) women in low- and middle - income countries . the prevalence of ckd ( both stages 15 and stages 35 ) increased with age ( figure 2 ) . subsequently , women had higher prevalences than men in middle - age groups , and this sex - difference became even greater in older age groups , especially for stages 35 . the pattern of age - related increase in ckd prevalence in men and women was consistent in high - income and low- and middle - income countries ( table 2 ) . in general , age - specific prevalences of ckd were higher in low- and middle - income countries compared to high - income countries , except in those aged 70 years , whose prevalence was higher in high - income countries for both men and women . the absolute numbers of men and women with ckd were much greater in low- and middle - income countries compared to high - income countries . approximately 78.6% of men and 77.3% of women with ckd stage 15 and 74.1% of men and 67.5% of women with ckd stage 35 were living in low- and middle - income countries . our analysis indicated that over 497 million adults aged 20 years and older in the world had ckd stages 15 in 2010 . of them , 236 million had moderate or severe decreases in kidney function , i.e. , ckd stages 35 . the majority of individuals with ckd were living in low- and middle - income countries . the age - adjusted prevalences of ckd were higher in low- and middle - income countries compared to high - income countries . our results also suggest that women had a higher prevalence of ckd and that prevalences increased with age consistently in high - income and low- and middle - income countries . however , the estimates in our analysis are limited by available data from published studies , including the use of only a single creatinine measurement to calculate estimated glomerular filtration rate ( egfr ) . it has been suggested that creatinine - based equations might systematically underestimate the true gfr , particularly among individuals with higher gfr levels ( 60 ml / min per 1.73 m ) ( 44 ) . in addition , the majority of population - based surveys did not follow patients for 3 months to confirm ckd . eriksen and ingebretsen reported that among 6,863 individuals in the municipality of troms with an initial egfr of 3059 ml / min/1.73 m , 2,175 ( 31.7% ) had subsequent estimates 60 ml / min/1.73 m within 3 months ( 45 ) . it is uncertain whether these findings are applicable to other populations with different races / ethnicities , geographic regions , and diets . nevertheless , these data indicate that a single measure of egfr may substantially overestimate the prevalence of ckd due to false positives . the high prevalence of ckd worldwide has led to an increased prevalence of esrd and mortality from cvd ( 13 ) . it was estimated that more than 1.9 million esrd patients were on renal replacement therapy in 2010 ( 5 ) . esrd causes reduced life expectancy and poor quality of life in patients and presents an enormous financial burden to families and society as a whole ( 1,6 ) . cvd is the leading cause of death in the world , and ischemic heart disease and stroke collectively killed 12.9 million people in 2010 , which represents one in four deaths worldwide ( 4 ) . both reduced gfr and albuminuria or proteinuria are associated with increased risk of esrd , cvd and premature death ( 2,3 ) . therefore , the prevention , detection , and treatment of ckd should be an effective approach for reducing esrd , cvd , and total mortality in the world . our study reported a high prevalence of ckd in the elderly , especially for ckd stages 35 . this high prevalence of ckd is mirrored by an increased number of elderly on kidney dialysis ( 46 ) . the national kidney foundation kidney disease outcomes quality initiative ( nkf kdoqi ) or the kidney disease : improving global outcomes ( kdigo ) clinical guidelines were used to define ckd in studies included in this analysis ( 47,48 ) . the appropriateness of egfr < 60 ml / min/1/73 m as the cut - point for ckd in the elderly is debatable since older age is associated with a physiological decline in gfr , and moderately reduced gfr might have less risk predictive value for esrd , cvd , and total mortality in the elderly ( 44,49 ) . therefore , use of a non - age - specific threshold for gfr to define ckd is most likely to substantially overestimate ckd prevalence in older age groups . further studies are warranted to define an appropriate gfr threshold for ckd in the elderly . our study also documented that women had a higher prevalence of ckd than men , and the gender difference was more pronounced in older age groups . these findings are consistent with large , nationally - representative studies from the united states , finland , and china ( 12,29,33 ) . data from the us national health and nutrition examination survey ( nhanes ) showed that the higher prevalence of ckd in women compared to men was consistent when egfr was calculated based on the modification of diet in renal disease ( mdrd ) equation , chronic kidney disease epidemiology collaboration ( ckd - epi ) creatinine - based equation , and ckd - epi cystatin c - based equation ( 6 ) . however , the prevalence and incidence of esrd are significantly higher in men than in women ( 6 ) . one possible explanation for this discrepancy is a faster progression of ckd to esrd in men compared to women ( 45 ) . our findings indicated that ckd affected many more individuals in low- and middle - income countries than in high - income countries . a higher prevalence of ckd and a much larger population resulted in a considerably greater absolute burden of ckd in low- and middle - income countries . in fact , more than three quarters of patients with ckd were living in low- and middle - income countries in 2010 . lifestyle changes due to rapid urbanization and globalization have led to the increased prevalence of ckd risk factors in low- and middle - income countries , while limited healthcare resources result in extremely low treatment and control rates of ckd risk factors in those countries ( 7,8 ) . our study results call for global collaborative efforts to combat ckd in low- and middle - income countries . the world health organization global action plan for the prevention and control of noncommunicable diseases 20132020 mentions kidney disease as a condition associated with two of its main diseases of interest , cvd and diabetes , but does not include ckd as a main priority ( 50 ) . the worldwide epidemics of diabetes and hypertension have likely played a major role in the increased global burden of ckd ( 1,7,8 ) . in addition , changes in lifestyle risk factors , environmental exposures , and the aging of the population have all likely contributed to the increased burden of ckd ( 1 ) . these risk factors are also associated with an increased risk of esrd , cvd , and total mortality in patients with ckd . despite having an estimated prevalence similar to diabetes in many countries , much less attention and resources have been allocated to ckd surveillance , prevention , and management compared with many other chronic diseases ( 51 ) . to reduce the global burden of ckd and related morbidities and mortalities , a comprehensive approach is needed that focuses on several inter - related risks to health , including hypertension , high ldl cholesterol , tobacco use , obesity , physical inactivity , poor diet , and diabetes ( 1,47,48 ) . in conclusion , our findings indicate that ckd is an important global - health challenge , especially in low- and middle - income countries . national and international efforts on the prevention , detection , and treatment of ckd are needed to reduce its morbidities and mortalities worldwide . literature search , study selection , and data extraction were conducted independently and in duplicate by at least two investigators using a standardized protocol and data - collection form . we searched medline using key words  prevalence  ,  cross - sectional study  ,  survey  ,  renal insufficiency ,  renal disease  ,  chronic kidney disease  ,  kidney function  ,  glomerular filtration rate  ,  albuminuria  and  proteinuria  . the search was restricted to studies in humans published from january 1 , 1990 , to december 31 , 2014 . a manual search was performed using references cited in reviews and original research articles . in addition , we searched projects awarded by the international society of nephrology global outreach program from 2005 , when the first clinical research program projects were funded , to 2014 . eligibility criteria for inclusion were : ( 1 ) population - based original studies in which prevalence of ckd ( or data to calculate it ) was reported ; ( 2 ) sex- and age - specific prevalence of ckd was provided ; ( 3 ) ckd was defined according to the nkf kdoqi or kdigo guidelines ( 47,48 ) and ( 4 ) serum creatinine values were standardized . the nkf kdoqi guidelines were selected because most nationally representative studies reporting ckd prevalence use these guidelines to define ckd . if a national study was available for a country , we used its data . if not , we used data from the largest and most recent multisite or regional study . if data from multiple regional studies within a country were available ( 15,16,30,31 ) , they were pooled to provide national estimates by weighting by age- and sex - specific sample size . if the most recent prevalence estimates were not published and if study datasets were available , age- and gender - specific prevalence estimates were calculated from the datasets . we calculated age- and sex - specific prevalence of ckd stages 15 and stages 35 in the us population using data from nhanes 20072012 ( 29 ) and ckd stages 35 in argentina and uruguay using data from the study on the detection and follow - up of cardiovascular disease and risk factors in the southern cone of latin america ( cescas ) ( 30 ) . if egfr from multiple equations was reported , we preferred the ckd - epi equation over the mdrd equation . likewise , we preferred urinary albumin excretion 30 mg / day ( or albumin - to - creatinine ratio 30 mg / g ) over urinary protein excretion 300 mg / day or a positive dipstick test of 1 + or greater to define kidney damage if multiple markers were reported . ckd stages 15 was defined as kidney damage or egfr < 60 ml / min/1.73 m , while ckd stages 35 was defined as egfr < 60 ml / min/1.73 m ( 47 ) . countries were grouped into high - income countries and low- and middle - income countries using the world bank classification system updated in july 2013 ( 52 ) . high - income countries are defined as those with a gross national income ( gni ) of $ 12,616 or more , and low - and middle - income countries are those with a gni less than $ 12,616 ( 52 ) . for countries without prevalence estimates meeting our inclusion criteria , we applied data from the country with the closest geographic proximity within the same geographical region defined using the world bank classification system ( 52 ) . if more than one country with data neighbored a country with no data , the country with the most similar gni was used . not all studies provided prevalence data for the full age range under consideration ( from 2029 years to 70 years ) . incomplete age - specific prevalence was estimated using logistic regression to model the relationship between age and prevalence of ckd for each sex in high - income countries and low- and middle - income countries , separately . median age and prevalence of ckd within each reported age group from available studies were used to create the predictive models . goodness of fit was tested by cragg and uhler 's pseudo r - square , and all models were well fit in high - income countries ( r between 0.55 and 0.84 ) and had poorer fit in low- and middle - income countries ( r between 0.27 and 0.59 ) . the prevalence and mean age in men and women from each study with missing age - specific prevalence were used to calibrate the predictive equation before it was used to estimate the age - specific prevalence for that country . if studies did not provide age - specific data in the 10-year increments of interest ( i.e. , 2029 , 3039 , etc ) , we averaged the prevalence from the two closest 10-year age groups weighting by age - specific population size from the country to estimate the prevalence of ckd for the age ranges of interest . for countries that reported only the prevalence of ckd stages 35 , logistic regression was used to predict the age - specific prevalence of stages 15 in men and women for high - income countries and low- and middle - income countries , separately . eight high - income countries ( 48 age - specific prevalence estimates ) and five low - income countries ( 30 age - specific prevalence estimates ) reported both prevalence of ckd stages 15 and stages 35 in men and women . these data were used to generate the predictive models for ckd stages 15 prevalence estimates from the age - specific prevalence of ckd stages 35 . for studies that reported only the prevalence of ckd stages 15 , these models all had good fit assessed by cragg and uhler 's pseudo r - square ( r between 0.56 and 0.89 ) . sex- and age - specific prevalences of ckd for each country were applied to the who sex- and age - specific population counts in 2010 to estimate the number of people with ckd in the country for each sex- and age - group ( 53 ) . the total number of persons with ckd in high - income countries and low- and middle - income countries was summed separately to provide an estimate of the total number of persons with ckd for each income category by sex- and age - groups , and the number from each income category was added to obtain the worldwide count . the sex- and age - specific prevalences of ckd for 2010 in high - income countries and low- and middle - income countries were calculated by dividing the total number of people with ckd in each income category by the number of people in that income category by sex- and age - groups . worldwide prevalence was estimated by dividing the total number of persons with ckd by the total adult world population . the prevalences of ckd in high - income countries and low- and middle - income countries were standardized by age to the 2010 world population separately for each sex and overall using the direct method . confidence intervals for all prevalence estimates were calculated using bootstrap methods ( 54 ) . for each prevalence estimate , we chose n studies , where n is the number of countries used to estimate that prevalence estimate , with replacement and calculated a mean prevalence . then we repeated this process 10,000 times and choose the values at 2.5% and 97.5% of the distribution as our bootstrap 95% confidence intervals . confidence intervals for all absolute burden estimates were calculated by multiplying the bootstrap 95% confidence intervals by the population for that prevalence estimate to get the 95% confidence intervals for the number of people with ckd . all analyses were done using sas ( version 9.3 ) , r ( version 3.1.2 ) , and microsoft excel software . we searched medline using key words  prevalence  ,  cross - sectional study  ,  survey  ,  renal insufficiency ,  renal disease  ,  chronic kidney disease  ,  kidney function  ,  glomerular filtration rate  ,  albuminuria  and  proteinuria  . the search was restricted to studies in humans published from january 1 , 1990 , to december 31 , 2014 . in addition , we searched projects awarded by the international society of nephrology global outreach program from 2005 , when the first clinical research program projects were funded , to 2014 . eligibility criteria for inclusion were : ( 1 ) population - based original studies in which prevalence of ckd ( or data to calculate it ) was reported ; ( 2 ) sex- and age - specific prevalence of ckd was provided ; ( 3 ) ckd was defined according to the nkf kdoqi or kdigo guidelines ( 47,48 ) and ( 4 ) serum creatinine values were standardized . the nkf kdoqi guidelines were selected because most nationally representative studies reporting ckd prevalence use these guidelines to define ckd . if a national study was available for a country , we used its data . if not , we used data from the largest and most recent multisite or regional study . if data from multiple regional studies within a country were available ( 15,16,30,31 ) , they were pooled to provide national estimates by weighting by age- and sex - specific sample size . if the most recent prevalence estimates were not published and if study datasets were available , age- and gender - specific prevalence estimates were calculated from the datasets . we calculated age- and sex - specific prevalence of ckd stages 15 and stages 35 in the us population using data from nhanes 20072012 ( 29 ) and ckd stages 35 in argentina and uruguay using data from the study on the detection and follow - up of cardiovascular disease and risk factors in the southern cone of latin america ( cescas ) ( 30 ) . if egfr from multiple equations was reported , we preferred the ckd - epi equation over the mdrd equation . likewise , we preferred urinary albumin excretion 30 mg / day ( or albumin - to - creatinine ratio 30 mg / g ) over urinary protein excretion 300 mg / day or a positive dipstick test of 1 + or greater to define kidney damage if multiple markers were reported . ckd stages 15 was defined as kidney damage or egfr < 60 ml / min/1.73 m , while ckd stages 35 was defined as egfr < 60 ml / min/1.73 m ( 47 ) . countries were grouped into high - income countries and low- and middle - income countries using the world bank classification system updated in july 2013 ( 52 ) . high - income countries are defined as those with a gross national income ( gni ) of $ 12,616 or more , and low - and middle - income countries are those with a gni less than $ 12,616 ( 52 ) . for countries without prevalence estimates meeting our inclusion criteria , we applied data from the country with the closest geographic proximity within the same geographical region defined using the world bank classification system ( 52 ) . if more than one country with data neighbored a country with no data , the country with the most similar gni was used . not all studies provided prevalence data for the full age range under consideration ( from 2029 years to 70 years ) . incomplete age - specific prevalence was estimated using logistic regression to model the relationship between age and prevalence of ckd for each sex in high - income countries and low- and middle - income countries , separately . median age and prevalence of ckd within each reported age group from available studies were used to create the predictive models . goodness of fit was tested by cragg and uhler 's pseudo r - square , and all models were well fit in high - income countries ( r between 0.55 and 0.84 ) and had poorer fit in low- and middle - income countries ( r between 0.27 and 0.59 ) . the prevalence and mean age in men and women from each study with missing age - specific prevalence were used to calibrate the predictive equation before it was used to estimate the age - specific prevalence for that country . if studies did not provide age - specific data in the 10-year increments of interest ( i.e. , 2029 , 3039 , etc ) , we averaged the prevalence from the two closest 10-year age groups weighting by age - specific population size from the country to estimate the prevalence of ckd for the age ranges of interest . for countries that reported only the prevalence of ckd stages 35 , logistic regression was used to predict the age - specific prevalence of stages 15 in men and women for high - income countries and low- and middle - income countries , separately . eight high - income countries ( 48 age - specific prevalence estimates ) and five low - income countries ( 30 age - specific prevalence estimates ) reported both prevalence of ckd stages 15 and stages 35 in men and women . these data were used to generate the predictive models for ckd stages 15 prevalence estimates from the age - specific prevalence of ckd stages 35 . for studies that reported only the prevalence of ckd stages 15 , these models all had good fit assessed by cragg and uhler 's pseudo r - square ( r between 0.56 and 0.89 ) . sex- and age - specific prevalences of ckd for each country were applied to the who sex- and age - specific population counts in 2010 to estimate the number of people with ckd in the country for each sex- and age - group ( 53 ) . the total number of persons with ckd in high - income countries and low- and middle - income countries was summed separately to provide an estimate of the total number of persons with ckd for each income category by sex- and age - groups , and the number from each income category was added to obtain the worldwide count . the sex- and age - specific prevalences of ckd for 2010 in high - income countries and low- and middle - income countries were calculated by dividing the total number of people with ckd in each income category by the number of people in that income category by sex- and age - groups . worldwide prevalence was estimated by dividing the total number of persons with ckd by the total adult world population . the prevalences of ckd in high - income countries and low- and middle - income countries were standardized by age to the 2010 world population separately for each sex and overall using the direct method . confidence intervals for all prevalence estimates were calculated using bootstrap methods ( 54 ) . for each prevalence estimate , we chose n studies , where n is the number of countries used to estimate that prevalence estimate , with replacement and calculated a mean prevalence . then we repeated this process 10,000 times and choose the values at 2.5% and 97.5% of the distribution as our bootstrap 95% confidence intervals . confidence intervals for all absolute burden estimates were calculated by multiplying the bootstrap 95% confidence intervals by the population for that prevalence estimate to get the 95% confidence intervals for the number of people with ckd . all analyses were done using sas ( version 9.3 ) , r ( version 3.1.2 ) , and microsoft excel software .