Prevalence of Diabetes Mellitus in School-age Children in Minnesota Carole J. Kyllo, M.P.H., and Frank Q. Nuttall, M.D., Ph.D., Minneapolis
SUMMARY
The prevalence of diabetes in Minnesota school-age children was found to be one per 529 students (1.89 per 1,000), 95 per cent of whom were receiving insulin. Data were obtained by a mail survey of the public schools in the state. Enrollment in public schools represents 90 per cent of the student population in Minnesota, and data were received from 96 per cent of the public schools. This return rate by schools accounts for 95 per cent of the total student enrollment. Diabetes increased linearly with age, representing a yearly prevalence increase of 0.16 cases per 1,000 students. DIABETES 27:57-60, January, 1978. INTRODUCTION
Diabetes mellitus has been considered to be an uncommon disease in childhood. However, few studies have attempted to document the prevalence of diabetes in children in this country. The National Health Interview Survey, conducted in 1965-66 by the United States Public Health Service, reported a prevalence of 1.6 per 1,000 of those under 25 years of age. 1 Since sample size was small, the reliability of these figures is questionable. The Report of the National Commission on Diabetes to the Congress of the United States indicates a prevalence of 1.3 per 1,000 or one per 744 for those under 17 years of age in the 1973 United States civilian noninstitutionalized population. 2 A study by Sultz, covering the period from 1946 to 1961, reported the prevalence of diabetes to be one per 1,626 children under 15 years (0.6 per 1,000) in Erie County, N.Y. 3 For some time we have had the impression that diabetes is more common in Minnesota children than would be expected from data in the literature. In a preliminary survey of children in one school district a From the Department of Public Health Nursing, School of Public Health, University of Minnesota, the Endocrinology Section, VA Hospital, Minneapolis, and the Department of Medicine, University of Minnesota. Address reprint requests to Carole J. Kyllo, M.P.H., 5201 Schaefer Road, Edina, Minn. 55436. Accepted for publication September 2, 1977. JANUARY, 1978
prevalence of approximately 1:600 students was found. A verbal report by Dr. Kurt Gorwitz indicating a prevalence of 1:611 students in grades kindergarten through 12 in Michigan, which subsequently has been published, 4 further stimulated us to conduct a formal survey of public school children in Minnesota. Data from this survey form the basis for this report. METHODS
In January of 1975, survey forms were mailed to the 1,85 1 public schools in Minnesota; they represent 913,958 students in 442 districts and 87 counties. About 90 per cent of all primary and secondary school children in the state are enrolled in public schools. Collection of surveys was completed in May of 1.975. Responses were received from 1,771 of the public schools: This is a 96 per cent return rate by schools and accounts for 95 per cent of the state public school enrollment. The survey form requested information concerning basic population-at-risk data, such as total student population and census distribution by sex and grade, as well as questions pertaining to the health care system of the schools. In addition, further data were requested on all reported diabetics regarding their birth date, sex, race, year of diagnosis, and medication. The data were keypunched in IBM cards and programed on a CDC 3.300 computer. Statistical consultation was provided by the Biometry Division, School of Public Health. RESULTS There were 1,644 diabetics reported among the 871,095 students. This is a rate of 1.89 per 1,000 students, or one per 529. A literature review indicates this to be the highest prevalence for this age group in the United States. Analysis of diabetes prevalence by sex was made of 679,789 of the original 871,095 students (78 per 57
CAROLE J. KYLLO, M.P.H.,-AND FRANK Q. NUTTAL, M.D., PH.D.
3.0
TABLE 2
2.8
Reported medication among diabetic students (Minnesota, 1975)
2.6 Type of medication Insulin Oraldrug None No response
2.4 2.2 2.0
Rate 1000
1.8 1.6
1.4 1.2 1.0 .8 £ A .2 AGE 0
I
2 3 4
S 6
GRADE K I
7 8 9 10 II 12 13 14 15 16 17 2 3 4 5 6 7 8 9
10 II 12
FIG. 1. Prevalence rates for diabetes mellitus by grade: The solid line represents actual numbers obtained. The broken line indicates the slope as determined by least-squares' analysis.
cent), as distribution of the student population by sex was not supplied by some schools. There were 644 female diabetics and 656 male diabetics among 333,035 female and 346,754 male students. The prevalences per 1,000 females and males were 1.93 TABLE 1 Distribution and prevalence rates of diabetes by grade (Minnesota, 1974-1975)
Grade K 1 2 3 4 5 6 7 8 9 10 11 12
58
Total number of cases 40 48 64 60 78 117 128 124 163 172 191 188 160 Totals.. . 1,533
Population at risk 57,422 52,968 52,440 53,852 57,327 61,167 64,914 69,728 70,703 71,936 72,566 67,302 63,903 816,228
%of total population 7.04 6.49 6.42 6.60 7.02 7.49 7.95 8.54 8.66 8.81 8.89 " 8.24 7.83 100.0
Rate per 1,000 0.70 0.91 1.22 1.11 1.36 1.91 1.97 1.78 2.30 2.39 2.63 2.79 ,2.50 1.88
Number of diabetics 1,444 17 54 129 Totals .... 1,644
Frequency of use (%) 87.8 1.0 3.3 7.8 99.9
Adjusted frequency (%) 95.3 1.1 3.6 — 100.0
and 1.89, respectively. The ratio of female rate to male rate was 1.02. This ratio, as reported by Gorwitz, varied by age, but was 1.00 to 1.03 for all reported age groups. 4 The National Health Interview Survey has reported a ratio of 1.11 for persons under 25 years of age. 5 The distribution and prevalence of diabetes by grade was available for 816,228 of the original 871,095 students (94 per cent) represented in the returned surveys. These data are presented in figure 1 and table 1. As grade is closely related to age, the graph can be interpreted as showing a linear relationship between age and prevalence of diabetes. The correlation coefficient Is 0.97, and the slope indicates a yearly increment of 0.16 cases per 1,000 students. The prevalence was greatest in llth-grade students. In this age group a prevalence of 2.79 per 1,000 (one per 358) was found. Of those who responded to the medication question, 95.3 per cent were receiving insulin, 1.1 per cent were taking an oral drug, and 3.6 per cent were not receiving any medication (table 2). Data related to prevalence by race were not statistically reliable because of low populations-at-risk for those other than whites. Information concerning year of diagnosis was not employed as data were incomplete and validity was also in question. Regarding geographic distribution, prevalence was calculated for all 442 districts and 87 counties in Minnesota. Districts, however, are frequently composed of 100 or 200 students. Sampling errors are therefore very high for a disease with an expected prevalence of approximately one per 500. County data are somewhat more reliable, although nearly 70 per cent of all counties have student populations of less than 5,000. The prevalence of diabetes by county varied from a low of 0.33 per 1,000 for Aitkin County, with a student population of 2,842, to 4.68 per 1,000 students for Marshall County, with a population of 3,874. No attempt has been made to interpret these distributions because of the small sample sizes in DIABETES, VOL. 27, NO. 1
PREVALENCE OF DIABETES IN CHILDREN IN MINNESOTA
many counties. Two questions were asked regarding health-care and record-keeping systems in the schools. First, "Does this school have a health form completed or updated on a yearly basis for each student?" The objective, in part, was to determine the accuracy of case reporting. It seems likely that a diabetic student would be identified in the routine of initiating or updating a health record. Over 80 per cent of schools claimed to do so on a yearly basis (table 3). The second question, "Do you feel it is likely there are diabetic children in this school of whom you are not aware?" also had implications related to accuracy or completeness of reported data. The responses indicated an assurance on the part of 70 per cent of those completing the questionnaire that their data are complete for diabetics. It is possible that equivocal responses originated with the high schools, where less reliable reporting is likely (table 4). DISCUSSION This study of prevalence of diabetes in school-age children is based on data obtained from the public schools. Since 90 per cent of students from kindergarten through 12th grade in this state attend public schools, sample representativeness should not be a limitation. The main difference between students in public and private schools was assumed to be socioeconomic. Sultz3 examined the relationship of diabetes mellitus to socioeconomic status and concluded there was little correlation. Other potential sources of error in the present study are definition of the disease, accuracy of school records, and medical background of the individuals completing the forms. A rigid criteria for the diagnosis of diabetes was not requested. Variations in diagnostic acumen are possible, and no attempt was made to verify the diagnosis. However, it is unlikely that an TABLE 3 Question 1: Does this school have a health form completed or updated on a yearly basis for each student?
Responses Yes No For some students No response Totals
Number 1,078 91 130 28 1,327*
%of total 81.2 6.9 9.8 2.1 100.0
*The total of 1,327 is less than the total of 1,771 responding schools because some school systems combined the data for several schools onto one form. JANUARY, 1978
TABLE 4 Question 2: Do you feel it is likely there are diabetic children in this school of whom you are not aware?
Responses Yes No Not sure No
response Totals
Number 81 934 287 25 1,327
%of total 6.1 70.4 21.6 1.9 100.0
overestimation of the disease has occurred, since 95 per cent of the diabetics were taking insulin. Inaccurate school records could generate spuriously low prevalences. This is more apt to occur in the high-school grades, where students are reluctant to report their disease for social reasons. Nevertheless, large errors in reporting are unlikely, since 80 per cent of the schools update health records on a yearly basis. In most instances, reporting was very likely done by the school nurses. In some cases, however, the facts were given by individuals with little medical experience, such as principals, secretaries, and aides. This may affect the data in that persons not directly occupied with the health care of the student would be less aware of diabetic individuals and their problems. Because of the cooperation of 96 per cent of the Minnesota public schools, the data presented should be an accurate representation of the diabetic status of school-age students in this state. The prevalence rate is higher than other reports from this country1"4 but is similar to those from several northern European countries. 6 " 8 These results indicate a need for more accurate national statistics on diabetes prevalence in the young. It is likely that diabetes mellitus is one of the most common chronic diseases of childhood. ACKNOWLEDGMENTS This study was endorsed by the State Commissioner of Education, the School Nurses Organization of Minnesota, the Twin Cities Diabetes Association, and the American Diabetes Association of Minnesota. This work was supported by a grant from the American Diabetes Association of Minnesota. The data have been taken from a dissertation submitted by Carole J. Kyllo to the School of Public Health of the University of Minnesota in partial fulfillment of the requirements for a Master of Public Health degree. The authors wish to thank Mary C. Gannon for assistance in the preparation of this manuscript. 59
CAROLE J. KYLLO, M.P.H., AND FRANK Q. NUTTAL, M.D., PH.D.
REFERENCES 'Vavra, Helen M.: Diabetes Source Book. USPHS Publication 1168. Washington, D.C., Government Printing Office, 1968. 2 U.S. Dept. HEW, PHS;, NIH: Report of the National Commission on Diabetes to the Congress of the United States. Vol. Ill, Part I, DHEW Publication (NIH)76-1021, 1975, Bethesda, Md., table I, p. 71. * 3 Sultz, Harry, Schlesinger, Edward, Mosher, William, and Feldman, Joseph: Long-term Childhood Illness. Pittsburgh, University of Pittsburgh Press, 1972, pp. 223-47. 4 Gorwitz, K., Howen, G. G., and Thompson, T.: Prevalence of diabetes in Michigan school-age children. Diabetes 25:122-27, 1976.
5 National Center for Health Statistics: Characteristics of Persons with Diabetes, United States, July, 1964-June, 1965. USPHS Publication, Ser. 10, No. 40, October 1967. Washington, D.C., U.S. Government Printing Office. 6 Wadsworth, M. E. J., and Jarrett, R. J.: Incidence of diabetes in the first 26 years of life. Lancet 2:1172-74, 1974. 7 Holmgren, G., Samuelson, G., and Hermansson, B.: The prevalence of diabetes mellitus: A study of children and their relatives in a northern Swedish county. Clin. Genet. .5:465-68, 1974. 8 Teuscher, A., Auckenthaler, R., Ehrengruber, H., Gasser, M., Hiisler, J., and Richterich, R.: Prevalence of latent diabetes in a juvenile population (diagnosis, methodology and interpretation). Klin. Wochenschr. .52:881, 1974 (Eng. abstr.).
1 I
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DIABETES, VOL. 27, NO. 1
SUMMARY
The prevalence of diabetes in Minnesota school-age children was found to be one per 529 students (1.89 per 1,000), 95 per cent of whom were receiving insulin. Data were obtained by a mail survey of the public schools in the state. Enrollment in public schools represents 90 per cent of the student population in Minnesota, and data were received from 96 per cent of the public schools. This return rate by schools accounts for 95 per cent of the total student enrollment. Diabetes increased linearly with age, representing a yearly prevalence increase of 0.16 cases per 1,000 students. DIABETES 27:57-60, January, 1978. INTRODUCTION
Diabetes mellitus has been considered to be an uncommon disease in childhood. However, few studies have attempted to document the prevalence of diabetes in children in this country. The National Health Interview Survey, conducted in 1965-66 by the United States Public Health Service, reported a prevalence of 1.6 per 1,000 of those under 25 years of age. 1 Since sample size was small, the reliability of these figures is questionable. The Report of the National Commission on Diabetes to the Congress of the United States indicates a prevalence of 1.3 per 1,000 or one per 744 for those under 17 years of age in the 1973 United States civilian noninstitutionalized population. 2 A study by Sultz, covering the period from 1946 to 1961, reported the prevalence of diabetes to be one per 1,626 children under 15 years (0.6 per 1,000) in Erie County, N.Y. 3 For some time we have had the impression that diabetes is more common in Minnesota children than would be expected from data in the literature. In a preliminary survey of children in one school district a From the Department of Public Health Nursing, School of Public Health, University of Minnesota, the Endocrinology Section, VA Hospital, Minneapolis, and the Department of Medicine, University of Minnesota. Address reprint requests to Carole J. Kyllo, M.P.H., 5201 Schaefer Road, Edina, Minn. 55436. Accepted for publication September 2, 1977. JANUARY, 1978
prevalence of approximately 1:600 students was found. A verbal report by Dr. Kurt Gorwitz indicating a prevalence of 1:611 students in grades kindergarten through 12 in Michigan, which subsequently has been published, 4 further stimulated us to conduct a formal survey of public school children in Minnesota. Data from this survey form the basis for this report. METHODS
In January of 1975, survey forms were mailed to the 1,85 1 public schools in Minnesota; they represent 913,958 students in 442 districts and 87 counties. About 90 per cent of all primary and secondary school children in the state are enrolled in public schools. Collection of surveys was completed in May of 1.975. Responses were received from 1,771 of the public schools: This is a 96 per cent return rate by schools and accounts for 95 per cent of the state public school enrollment. The survey form requested information concerning basic population-at-risk data, such as total student population and census distribution by sex and grade, as well as questions pertaining to the health care system of the schools. In addition, further data were requested on all reported diabetics regarding their birth date, sex, race, year of diagnosis, and medication. The data were keypunched in IBM cards and programed on a CDC 3.300 computer. Statistical consultation was provided by the Biometry Division, School of Public Health. RESULTS There were 1,644 diabetics reported among the 871,095 students. This is a rate of 1.89 per 1,000 students, or one per 529. A literature review indicates this to be the highest prevalence for this age group in the United States. Analysis of diabetes prevalence by sex was made of 679,789 of the original 871,095 students (78 per 57
CAROLE J. KYLLO, M.P.H.,-AND FRANK Q. NUTTAL, M.D., PH.D.
3.0
TABLE 2
2.8
Reported medication among diabetic students (Minnesota, 1975)
2.6 Type of medication Insulin Oraldrug None No response
2.4 2.2 2.0
Rate 1000
1.8 1.6
1.4 1.2 1.0 .8 £ A .2 AGE 0
I
2 3 4
S 6
GRADE K I
7 8 9 10 II 12 13 14 15 16 17 2 3 4 5 6 7 8 9
10 II 12
FIG. 1. Prevalence rates for diabetes mellitus by grade: The solid line represents actual numbers obtained. The broken line indicates the slope as determined by least-squares' analysis.
cent), as distribution of the student population by sex was not supplied by some schools. There were 644 female diabetics and 656 male diabetics among 333,035 female and 346,754 male students. The prevalences per 1,000 females and males were 1.93 TABLE 1 Distribution and prevalence rates of diabetes by grade (Minnesota, 1974-1975)
Grade K 1 2 3 4 5 6 7 8 9 10 11 12
58
Total number of cases 40 48 64 60 78 117 128 124 163 172 191 188 160 Totals.. . 1,533
Population at risk 57,422 52,968 52,440 53,852 57,327 61,167 64,914 69,728 70,703 71,936 72,566 67,302 63,903 816,228
%of total population 7.04 6.49 6.42 6.60 7.02 7.49 7.95 8.54 8.66 8.81 8.89 " 8.24 7.83 100.0
Rate per 1,000 0.70 0.91 1.22 1.11 1.36 1.91 1.97 1.78 2.30 2.39 2.63 2.79 ,2.50 1.88
Number of diabetics 1,444 17 54 129 Totals .... 1,644
Frequency of use (%) 87.8 1.0 3.3 7.8 99.9
Adjusted frequency (%) 95.3 1.1 3.6 — 100.0
and 1.89, respectively. The ratio of female rate to male rate was 1.02. This ratio, as reported by Gorwitz, varied by age, but was 1.00 to 1.03 for all reported age groups. 4 The National Health Interview Survey has reported a ratio of 1.11 for persons under 25 years of age. 5 The distribution and prevalence of diabetes by grade was available for 816,228 of the original 871,095 students (94 per cent) represented in the returned surveys. These data are presented in figure 1 and table 1. As grade is closely related to age, the graph can be interpreted as showing a linear relationship between age and prevalence of diabetes. The correlation coefficient Is 0.97, and the slope indicates a yearly increment of 0.16 cases per 1,000 students. The prevalence was greatest in llth-grade students. In this age group a prevalence of 2.79 per 1,000 (one per 358) was found. Of those who responded to the medication question, 95.3 per cent were receiving insulin, 1.1 per cent were taking an oral drug, and 3.6 per cent were not receiving any medication (table 2). Data related to prevalence by race were not statistically reliable because of low populations-at-risk for those other than whites. Information concerning year of diagnosis was not employed as data were incomplete and validity was also in question. Regarding geographic distribution, prevalence was calculated for all 442 districts and 87 counties in Minnesota. Districts, however, are frequently composed of 100 or 200 students. Sampling errors are therefore very high for a disease with an expected prevalence of approximately one per 500. County data are somewhat more reliable, although nearly 70 per cent of all counties have student populations of less than 5,000. The prevalence of diabetes by county varied from a low of 0.33 per 1,000 for Aitkin County, with a student population of 2,842, to 4.68 per 1,000 students for Marshall County, with a population of 3,874. No attempt has been made to interpret these distributions because of the small sample sizes in DIABETES, VOL. 27, NO. 1
PREVALENCE OF DIABETES IN CHILDREN IN MINNESOTA
many counties. Two questions were asked regarding health-care and record-keeping systems in the schools. First, "Does this school have a health form completed or updated on a yearly basis for each student?" The objective, in part, was to determine the accuracy of case reporting. It seems likely that a diabetic student would be identified in the routine of initiating or updating a health record. Over 80 per cent of schools claimed to do so on a yearly basis (table 3). The second question, "Do you feel it is likely there are diabetic children in this school of whom you are not aware?" also had implications related to accuracy or completeness of reported data. The responses indicated an assurance on the part of 70 per cent of those completing the questionnaire that their data are complete for diabetics. It is possible that equivocal responses originated with the high schools, where less reliable reporting is likely (table 4). DISCUSSION This study of prevalence of diabetes in school-age children is based on data obtained from the public schools. Since 90 per cent of students from kindergarten through 12th grade in this state attend public schools, sample representativeness should not be a limitation. The main difference between students in public and private schools was assumed to be socioeconomic. Sultz3 examined the relationship of diabetes mellitus to socioeconomic status and concluded there was little correlation. Other potential sources of error in the present study are definition of the disease, accuracy of school records, and medical background of the individuals completing the forms. A rigid criteria for the diagnosis of diabetes was not requested. Variations in diagnostic acumen are possible, and no attempt was made to verify the diagnosis. However, it is unlikely that an TABLE 3 Question 1: Does this school have a health form completed or updated on a yearly basis for each student?
Responses Yes No For some students No response Totals
Number 1,078 91 130 28 1,327*
%of total 81.2 6.9 9.8 2.1 100.0
*The total of 1,327 is less than the total of 1,771 responding schools because some school systems combined the data for several schools onto one form. JANUARY, 1978
TABLE 4 Question 2: Do you feel it is likely there are diabetic children in this school of whom you are not aware?
Responses Yes No Not sure No
response Totals
Number 81 934 287 25 1,327
%of total 6.1 70.4 21.6 1.9 100.0
overestimation of the disease has occurred, since 95 per cent of the diabetics were taking insulin. Inaccurate school records could generate spuriously low prevalences. This is more apt to occur in the high-school grades, where students are reluctant to report their disease for social reasons. Nevertheless, large errors in reporting are unlikely, since 80 per cent of the schools update health records on a yearly basis. In most instances, reporting was very likely done by the school nurses. In some cases, however, the facts were given by individuals with little medical experience, such as principals, secretaries, and aides. This may affect the data in that persons not directly occupied with the health care of the student would be less aware of diabetic individuals and their problems. Because of the cooperation of 96 per cent of the Minnesota public schools, the data presented should be an accurate representation of the diabetic status of school-age students in this state. The prevalence rate is higher than other reports from this country1"4 but is similar to those from several northern European countries. 6 " 8 These results indicate a need for more accurate national statistics on diabetes prevalence in the young. It is likely that diabetes mellitus is one of the most common chronic diseases of childhood. ACKNOWLEDGMENTS This study was endorsed by the State Commissioner of Education, the School Nurses Organization of Minnesota, the Twin Cities Diabetes Association, and the American Diabetes Association of Minnesota. This work was supported by a grant from the American Diabetes Association of Minnesota. The data have been taken from a dissertation submitted by Carole J. Kyllo to the School of Public Health of the University of Minnesota in partial fulfillment of the requirements for a Master of Public Health degree. The authors wish to thank Mary C. Gannon for assistance in the preparation of this manuscript. 59
CAROLE J. KYLLO, M.P.H., AND FRANK Q. NUTTAL, M.D., PH.D.
REFERENCES 'Vavra, Helen M.: Diabetes Source Book. USPHS Publication 1168. Washington, D.C., Government Printing Office, 1968. 2 U.S. Dept. HEW, PHS;, NIH: Report of the National Commission on Diabetes to the Congress of the United States. Vol. Ill, Part I, DHEW Publication (NIH)76-1021, 1975, Bethesda, Md., table I, p. 71. * 3 Sultz, Harry, Schlesinger, Edward, Mosher, William, and Feldman, Joseph: Long-term Childhood Illness. Pittsburgh, University of Pittsburgh Press, 1972, pp. 223-47. 4 Gorwitz, K., Howen, G. G., and Thompson, T.: Prevalence of diabetes in Michigan school-age children. Diabetes 25:122-27, 1976.
5 National Center for Health Statistics: Characteristics of Persons with Diabetes, United States, July, 1964-June, 1965. USPHS Publication, Ser. 10, No. 40, October 1967. Washington, D.C., U.S. Government Printing Office. 6 Wadsworth, M. E. J., and Jarrett, R. J.: Incidence of diabetes in the first 26 years of life. Lancet 2:1172-74, 1974. 7 Holmgren, G., Samuelson, G., and Hermansson, B.: The prevalence of diabetes mellitus: A study of children and their relatives in a northern Swedish county. Clin. Genet. .5:465-68, 1974. 8 Teuscher, A., Auckenthaler, R., Ehrengruber, H., Gasser, M., Hiisler, J., and Richterich, R.: Prevalence of latent diabetes in a juvenile population (diagnosis, methodology and interpretation). Klin. Wochenschr. .52:881, 1974 (Eng. abstr.).
1 I
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DIABETES, VOL. 27, NO. 1
