Clin Ex Nehrol (202) 6:749 754 DOI 0.007/s057-02-0628-0 ORIGINAL ARTICLE Differences in the local and national revalences of chronic kidney disease based on annual health check rogram data Minako Wakasugi Junichiro James Kazama Ichiei Narita Received: 27 December 20 / Acceted: 3 March 202 / Published online: Aril 202 Ó Jaanese Society of Nehrology 202 Abstract Background Chronic kidney disease (CKD) is now recognized as a global ublic health roblem, and evaluating the revalence at the local level is imortant and helful for assessing health care needs and targeted interventions. To assess the current icture concerning CKD in a local area, local and national revalences were comared by calculating standardized rate ratios (SRRs) and confidence intervals (CIs). Methods For the national revalence, the data from a revious reort that showed age- and sex-secific revalence of each stage on the basis of a large dataset from the Jaanese annual health check rogram were used. Using annual health check rogram data in Sado City, the SRRs and CIs were calculated. Results The SRRs were 0.70 for males and 0.60 for females, indicating that Sado City had a 30 % lower revalence for males and a 40 % lower for females than the national average. The 95 % CIs of the SRRs were calculated as 0.64 0.72 for males and 0.55 0.64 for females. Thus, the revalence for both males and M. Wakasugi (&) Center for Inter-organ Communication Research, Niigata University Graduate School of Medical and Dental Sciences, Asahimachi -757, Chuo-ku, Niigata 95-850, Jaan e-mail: minakowa@med.niigata-u.ac.j J. J. Kazama Division of Blood Purification Theray, Niigata University Medical and Dental Hosital, Niigata, Jaan I. Narita Division of Clinical Nehrology and Rheumatology, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Jaan females in Sado City is significantly lower than the national average for Jaan. Conclusions Because this methodology adjusts for age and sex, it can serve as a useful tool to assess the current icture related to CKD in a local area. We believe that this could be an imortant ste for imroving local care to revent the develoment. Keywords Chronic kidney disease Confidence intervals General oulation Local area level Introduction Aroximately 3.3 million eole are estimated to have chronic kidney disease (CKD) in Jaan []. Because atients with CKD are a high-risk oulation not only for reaching endstage renal disease (ESRD) but also for cardiovascular disease and all-cause mortality [2, 3], it is a ublic health roblem of growing imortance. In addition, increasing numbers of ESRD atients ose a serious economic threat to local governments because the cost of ESRD treatment is high. CKD is an increasingly revalent roblem, esecially in societies with an aging oulation []. Sado City, an island located in the Sea of Jaan off the coast of Niigata Prefecture, is one of the areas with the most raidly aging oulation in Jaan. More than 35 % of the oulation is [65 years, of whom half are[75 years. This roortion of elderly is almost equal to the oulation rojection in Jaan in 2039 [4]. There is a comelling need for effective strategies against CKD. To revent the develoment and its rogression to ESRD, evaluation of the revalence at a local level is imortant for assessing the needs for health care and targeted interventions.
750 Clin Ex Nehrol (202) 6:749 754 In the resent study, to assess the current status in Sado City, the local and national revalences were comared by determining standardized rate ratios (SRRs) and confidence intervals (CIs). Methods The revalence was defined as a glomerular filtration rate (GFR)\60 ml/min/.73 m 2 as calculated using the estimated GFR (egfr) formula for Jaanese ersons as below [5]. egfr ¼ 94 serum creatinine :094 age 0:287 ð0:739 for femalesþ The national revalence was determined based on a revious reort that showed the age-secific revalence stages in both males (Table in []) and females (Table 2 in []) on the basis of a large dataset from the Jaanese annual health check rogram in 2005 []. In this reort, the revalence was estimated to be about 3 % of the Jaanese adult oulation, aroximately 3.3 million eole, using these data []. To comare the revalence at a local level with the national revalence, the number of atients exected to have CKD was calculated by multilying the number of males or females in each age grou from the target area by the corresonding age- and sex-secific national revalence. The results for all subgrous by each age and sex were totaled to give the exected number atients in the target area. Finally, each SRR was calculated as the ratio of the observed to the exected number. The SRR can be interreted as the relative trend of revalence in a local oulation comared with that of the national oulation. Of several methods of calculating CIs, the method used in the resent study yields fairly accurate results without requiring comlex calculations [6, 7] and allows CIs to be determined with a hand calculator. Calculation of the SRR for Sado City Data from a Secific Health Checkus and Guidance System ( aged \75 years) and health checku rograms for the elderly ( aged [75 years) conductedinsadocityin2008wereusedtocalculatethe exected number of atients with CKD. The Secific Health Checkus and Guidance System rogram and health checku rograms for the elderly have been described elsewhere [8]. In brief, answered a self-administered questionnaire that covered their medical history, smoking habits, alcohol intake, and exercise attern. Trained staff then measured the height, weight, blood ressure, and waist circumference of each articiant, after which serum and sot urine samles were collected. Although serum creatinine is generally not included in the mandatory items of the Secific Health Checkus and Guidance System of Jaan and health checku rograms for the elderly, it is uniquely included in the health check rogram in Sado City. Serum creatinine was measured using an enzymatic method. The actual number atients in Sado City was calculated from the data obtained from the rogram using the egfr formula. All of the remained anonymous and the study was conducted according to Jaanese rivacy rotection laws and the ethical guidelines for eidemiological studies ublished by the Ministry of Education, Science and Culture and the Ministry of Health, Labor and Welfare in 2005. All calculations could be erformed with a hand calculator. Microsoft Excel (Redmond, WA, USA) was used for easy calculation. Results The national revalences stratified by age and sex are shown in Table []. The overall national revalence Table of chronic kidney disease (CKD) by age and sex Males Females Number atients (%) Number atients (%) CKD is defined as an estimated glomerular filtration rate \60 ml/min/.73 m 2. Reroduced from Imai et al. [] 20 29 2 9,807 0.2 23 0,457 0.22 30 39 24 23,93 0.92 88 20,924 0.90 40 49,449 36,478 3.97,340 5,859 2.58 50 59 3,820 5,043 7.48 5,502 80,675 6.82 60 69 9,288 58,640 5.84 2,936 87,52 4.78 70 79 4,04 50,605 27.75 2,437 67,480 3.77 C80 4,834 0,828 44.64 6,694 4,54 46.2 Total 33,658 240,594 3.99 48,20 333,430 4.43
Clin Ex Nehrol (202) 6:749 754 75 was 3.99 % for males and 4.43 % for females. The revalence increased with age. A total of 53,938 residents (male 47 %) aged C20 years lived in Sado City as of October 2008. Of these, 3,942 males (6 %) and 5,506 females (9 %) articiated in the Jaanese secific health check and guidance system in 2008. The results of the calculations are listed in Table 2. The exected and observed numbers of with CKD were 850.2 and 595 for males and,2.2 and 722 for females, resectively. The SRRs were 0.70 for males and 0.60 for females, indicating that Sado City had a 30 % lower revalence for males and a 40 % lower revalence for females than that exected if the oulation had exerienced the same age-secific revalence rates of CKD as the reference oulation. The 95 % CIs of the SRRs were calculated as 0.64 0.72 for males and 0.55 0.64 for females. The CI rovides a lausible range for the true SRR. Since these 95 % CIs for the SRRs did not include.0, the null hyothesis of equality between the revalence of Sado City and the national rate can be rejected at the P = 0.05 level. Thus, the revalences of CKD for both males and females in Sado City are significantly lower than the national average for Jaan. Figure clearly shows that the revalence in Sado City was lower than the national average for both males and females by age subgrous. When the revalence was defined as a GFR \50 ml/min/.73 m 2, the study results remained similar (Tables 3 and 4). The SRR for males and females were 0.7 (95 % CI, 0.62 0.82) and 0.66 (95 % CI, 0.58 0.75), resectively. Discussion The resent study showed that the revalence in Sado City was significantly lower for both males and females than the Jaanese national average. This finding was somewhat surrising for health care rofessionals at Sado City Hall, because they had exected that the roortion atients would be high. Although we could not clarify the reasons why Sado City had a lower revalence than the national average in this study, some lifestyle factors would be associated with the lower revalence. To try to settle the issue, further study is now underway in cooeration with Sado City Hall. Of course, the screening rate of the health check rogram might affect these results. In addition, the might not have been reresentative of the general oulation, since they were generally concerned about their health and were in relatively good condition. However, the national data, uon which the comarisons of ratios were erformed, were also based on data from the annual health check rogram. Although this methodology has limitations, the current icture concerning CKD at the local level could be easily assessed by calculating the SRRs and CIs. In cooeration with Sado City Hall, we lan to increase the screening rate of the health check rogram and to re-evaluate these calculations in the coming years. Although the data from Sado City were used in the resent analysis, any local or regional data could be comared with national data using this method. From a ublic health ersective, screening for CKD to determine the revalence at a local level is imortant for assessing the needs for health care and interventions. Because CKD is common, harmful, and treatable [9], the issue extends beyond a clinical roblem addressed only by health care roviders to a major ublic health issue requiring multilevel efforts. Nehrologists need to work with health care rofessionals in local areas to develo ublic health aroaches to reduce the burden, and data and information must be rovided to health care olicy makers so that their decisions will effectively address CKD. In combination with the method we reviously reorted, which allowed comarison of the local to the national incidence of dialysis atients by determining a standardized incidence ratio and confidence intervals [0], we might be able to comrehensively evaluate local areas for managing CKD. Because the relationshi between the revalence and the incidence of ESRD is comlex [], estimating both the revalence of CKD and the incidence of ESRD is required for assessing the current status. One advantage of the SRR, which is calculated from the total number, is that age-secific incidence data are not required for its calculation. However, several cautions are needed. First, comarison of the SRRs between different local areas is invalid, because local areas show differences in the structure of their study oulations [6, 2]. Second, a relatively small number of could otentially have caused the difficulty in detection of the differences, which led to wide confidence intervals. Finally, the national average is just the mean value and should not be misinterreted as a standard of ideal care. We think that the resent study is only a first ste toward assessing the current status at a local level, with the next ste being a more focused comarison to identify the reasons for local differences. To determine the revalence at a local level, we recommend that serum creatinine be included as a mandatory item of the Secific Health Checkus and Guidance System of Jaan and health checku rograms for the elderly. Because there are many individuals with CKD who are unaware of this disorder, screening for CKD is one of the most imortant strategies [3]. The annual health
752 Clin Ex Nehrol (202) 6:749 754 Table 2 Examle of using Table (revalence ) to comare the local and national revalences Males Females Exected a b number atients c Observed number atients d SRR (95 % CI) Exected a e number atients f Observed number atients d SRR (95 % CI) 20 29 0.2 82 0. 0 NA 0.22 28 0.3 0 NA 30 39 0.92 42.3 0 NA 0.90 377 3.4 0 NA 40 49 3.97 75 6.9 4 0.58 (0.6,.48) 2.58 22 5.5 3 0.54 (0.,.60) 50 59 7.48 405 30.3 8 0.59 (0.35, 0.94) 6.82 494 33.7 39.6 (0.82,.58) 60 69 5.84,27 92.8 65 0.86 (0.73,.00) 4.78,695 250.5 6 0.64 (0.55, 0.75) 70 79 27.75,408 390.7 276 0.7 (0.63, 0.80) 3.77,957 62.7 264 0.42 (0.38, 0.48) C80 44.64 5 228. 32 0.58 (0.48, 0.69) 46.2 642 296. 255 0.86 (0.76, 0.97) Total 3.99 3,942 850.2 595 0.70 (0.64, 0.76) 4.43 5,506,2.2 722 0.60 (0.55, 0.64) Calculation of the standardized rate ratio (SRR) and 95 % confidence interval (CI) SRR: observed/exected = 595/850.2 = 0.70 (males); 722/,2.2 = 0.60 (females) 95 % CI:! Lower confidence limit: ¼ ðobservedþ 3 ðexectedþ 9ðObservedÞ :96 3 ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ðobservedþ ¼ 595 850:2 :96 3 9 595 3 ffiffiffiffiffiffiffi ¼ 722 595 2:2 :96 3 9 722 3 ffiffiffiffiffiffiffi 722 ¼ 0:64 ðmales Þ ¼ 0:55 ðfemales Þ Uer confidence limit: ¼ NA not available ðobserved þ Þ ðexectedþ ¼ 595 þ 850:2 9ðObserved + Þ :96 9 ð595 þ Þ :96 3 ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ð595 þ Þ 3 ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ðobserved + Þ! 3 ¼ 722 þ 2:2 ¼ 0:76 ðmales Þ ¼ 0:64 ðfemales Þ Percentage rates for the given age and sex subgrou from Table! 3 9 ð722 þ Þ :96 3 ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi ð722 þ Þ! 3 a b Enter the number of males having the local health check rogram stratified by age Calculated as (male revalence ) 9 (number of male )/00 c d Enter the number of local CKD atients stratified by age Enter the number of females in the local health check rogram stratified by age e Calculated as (female revalence ) 9 (number of female )/00 f
Clin Ex Nehrol (202) 6:749 754 753 checku is a good oortunity to screen for CKD, because it is erformed annually for the Jaanese general oulation. However, serum creatinine is not included in the mandatory items of the Secific Health Checkus and Guidance System of Jaan and health checku rograms for the elderly [8]. The resent study clearly demonstrated that measuring serum creatinine is useful not only for individual screening for CKD but also for ublic health evaluation at a local level. Some limitations of the method used in this study should be discussed. First, CKD was defined from a single creatinine value, and measurements of creatinine can vary Patients 500 400 300 200 00 0 700 600 500 400 300 200 00 0 Males Exected Observed 20-29 30-39 40-49 50-59 60-69 70-79 80 and over Females 20-29 30-39 40-49 50-59 60-69 70-79 80 and over Fig. Observed and exected number of with CKD in Sado City; exected: the number of redicted to have CKD in Sado City; observed: the actual number of with CKD in Sado City among different laboratories. It is not ossible to determine whether who fulfilled the CKD criteria did so for at least a 3-month eriod during this study. However, annual reeated measurements in the health check rogram could solve the roblem. Second, the national data were based on data acquired in 2005. With recent imrovements in the strategies for managing CKD, the revalence of CKD might have changed. Furthermore, the national data were reorted on the basis of a large dataset from the Jaanese annual health check rogram, but the entire oulation of Jaan was not included. To imrove the method described here, nationwide and regularly udated reference data are needed. Desite these limitations, this method has several strengths. First, it allows convenient comarison of local data with the national average. Second, the calculation of CIs was simle. Third, as the health check rogram collects data annually, sequential comarisons are ossible. Furthermore, this method allows comarison with data from other countries. The age- and sex-adjusted revalence of CKD can be calculated for another country and comared with the national revalence of Jaan. Finally, the results of this study may lead to re-evaluation of local efforts to revent CKD rogression. To imrove the method, we have three recommendations. First, the screening rate of the health check rogram in local areas must be increased. Second, nationwide and regularly udated reference data are needed. Finally, we recommend that serum creatinine should be included as a mandatory item of the Secific Health Checkus and Guidance System of Jaan and health checku rograms for the elderly. Conclusions A ractical method to estimate the number atients in local areas was resented. This method may be one way Table 3 of chronic kidney disease (CKD) by age and sex Males CKD atients of CKD (%) Females CKD atients of CKD (%) CKD is defined as an estimated glomerular filtration rate \50 ml/min/.73 m 2 Reroduced from Imai et al. [] 20 29 7 9,807 0.07 4 0,457 0.04 30 39 27 23,93 0.2 20 20,924 0.0 40 49 59 36,478 0.44 34 5,859 0.26 50 59 6 5,043.20 680 80,675 0.84 60 69 2,258 58,640 3.85 2,335 87,52 2.67 70 79 4,572 50,605 9.03 5,578 67,480 8.27 C80,970 0,828 8.9 3,309 4,54 22.80 Total 9,604 240,594 3.99 2,060 333,430 3.62
754 Clin Ex Nehrol (202) 6:749 754 Table 4 Examle of using Table 3 (revalence ) to comare the local and national revalences Males Females SRR (95 % CI) Observed number atients Exected number atients SRR (95 % CI) (%) Observed number atients Exected number atients (%) 20 29 0.07 82 0. 0 NA 0.04 28 0.0 0 NA 30 39 0.2 42 0.2 0 NA 0.0 377 0.4 0 NA 40 49 0.44 75 0.8 0 NA 0.26 22 0.5.83 (0.05, 0.2) 50 59.20 405 4.8 0 2.06 (0.99, 3.79) 0.84 494 4.2 2 0.48 (0.06,.74) 60 69 3.85,27 46.9 35 0.75 (0.52,.04) 2.67,695 45.2 5.3 (0.84,.48) 70 79 9.03,408 27.2 73 0.58 (0.45, 0.72) 8.27,957 6.8 02 0.63 (0.5, 0.77) C80 8.9 5 93.0 77 0.83 (0.65,.04) 22.80 642 46.4 8 0.55 (0.44, 0.69) Total 3.99 3,942 272.9 95 0.7 (0.62, 0.82) 3.62 5,506 358.5 237 0.66 (0.58, 0.75) CKD is defined as an estimated glomerular filtration rate \50 ml/min/.73 m 2 SRR standardized rate ratio, 95 % CI confidence interval, NA not available to rovide information that guides us in imroving local care to revent CKD. Acknowledgments The authors would like to thank the citizens of Sado City and Sado City Hall for ermission to use their data. This study was suorted in art by a Grant-in-Aid for Project in Sado for Total Health (PROST) from the Ministry of Education, Culture, Sorts, Science and Technology of Jaan, and also a Grant-in-Aid for Progressive Renal Diseases Research, Research on intractable diseases, from the Ministry of Health, Labour and Welfare of Jaan. Conflict of interest References None.. Imai E, Horio M, Watanabe T, Iseki K, Yamagata K, Hara S, Ura N, Kiyohara Y, Moriyama T, Ando Y, Fujimoto S, Konta T, Yokoyama H, Makino H, Hishida A, Matsuo S. of chronic kidney disease in the Jaanese general oulation. Clin Ex Nehrol. 2009;3:62 30. 2. Go AS, Chertow GM, Fan D, McCulloch CE, Hsu CY. Chronic kidney disease and the risks of death, cardiovascular events, and hositalization. N Engl J Med. 2004;35:296 305. 3. Irie F, Iso H, Sairenchi T, Fukasawa N, Yamagishi K, Ikehara S, Kanashiki M, Saito Y, Ota H, Nose T. The relationshis of roteinuria, serum creatinine, glomerular filtration rate with cardiovascular disease mortality in Jaanese general oulation. Kidney Int. 2006;69:264 7. 4. National Institute of Poulation and Social Security Research. htt://www.iss.go.j/-newest/j/newest03/h3_3.html. Accessed 3 Setember 20. 5. Matsuo S, Imai E, Horio M, Yasuda Y, Tomita K, Nitta K, Yamagata K, Tomino Y, Yokoyama H. Collaborators develoing the Jaanese equation for estimated GFR. Revised equations for estimated GFR from serum creatinine in Jaan. Am J Kidney Dis. 2009;53:982 92. 6. Breslow NE, Day NE. Rates and rate standardization. In: Statistical methods in cancer research, volume II: the design and analysis of cohort studies. Lyon: International ncy for Research on Cancer; 987.. 48 79. 7. Wolfe RA. The standardized mortality ratio revisited: imrovements, innovations, and limitations. Am J Kidney Dis. 994;24: 290 7. 8. Kohro T, Furui Y, Mitsutake N, Fujii R, Morita H, Oku S, Ohe K, Nagai R. The Jaanese national health screening and intervention rogram aimed at reventing worsening of the metabolic syndrome. Int Heart J. 2008;49:93 203. 9. Levey AS, Andreoli SP, DuBose T, Provenzano R, Collins AJ. Chronic kidney disease: common, harmful and treatable World Kidney Day 2007. Am J Kidney Dis. 2007;49:75 9. 0. Wakasugi M, Kazama JJ, Narita I. Use of Jaanese Society for Dialysis Theray dialysis tables to comare the local and national incidence of dialysis. Ther Aher Dial. 202;6:63 7.. Hallan SI, Vikse BE. Relationshi between chronic kidney disease revalence and end-stage renal disease risk. Curr Oin Nehrol Hyertens. 2008;7:286 9. 2. Julious SA, Nicholl J, George S. Why do we continue to use standardized mortality ratios for small area comarisons? J Public Health Med. 200;23:40 6. 3. Levey AS, Eckardt KU, Tsukamoto Y, Levin A, Coresh J, Rossert J, De Zeeuw D, Hostetter TH, Lameire N, Eknoyan G. Definition and classification of chronic kidney disease: a osition statement from Kidney Disease: Imroving Global Outcomes (KDIGO). Kidney Int. 2005;67:2089 00.