the search for diabetes in youth study ( search study ) ascertained diabetes in youth aged < 20 years in 2001 and continues to ascertain incident cases since 2002 ( 9 ) in geographically defined populations in ohio , washington , south carolina , and colorado and among health plan enrollees in hawaii and southern california . coordinated by the colorado center , diabetes cases were also identified among navajo youth . the search - navajo study sought to identify all prevalent cases of diabetes in 2001 and all incident cases in 20022005 . the study was approved by the indian health services ( ihs ) directors , directors of tribally operated health care facilities , and the navajo nation human research review board ( nnhrrb ) and was health insurance portability and accountability act compliant . the population denominator was defined as individuals aged < 20 years who self - identified themselves as navajo and had at least one visit in the preceding 3 years to an eligible health care facility . health care facilities include six navajo area his units ( chinle , crownpoint , fort defiance , gallup , kayenta , and shiprock ) and two tribally operated facilities ( tuba city and winslow ) . potential case subjects had one or more outpatient visits or hospitalizations coded for diabetes ( icd-9 codes 250.0250.9 ) and were aged < 20 years on 31 december 2001 . for 20022005 incidence estimates , the denominator included eligible youth with at least one visit in the preceding 3 calendar years . the sum of the annual denominators was used as average total denominator ( n = 380,633 person - years ) over the 4-year period . potential case subjects had one or more diabetes - related icd-9 codes , were diagnosed in 20022005 , and were aged < 20 years on 31 december of the year of diagnosis . less than 50% of case subjects identified using the ihs database had diabetes ; miscoding was the most common reason for invalid case reports . for all validated cases , core demographic and diagnostic information was obtained from medical records . the clinical diabetes type assigned by the health care provider was categorized as type 1 ( combining types 1 , 1a , and 1b ) and type 2 diabetes . youth with other types ( including hybrid , secondary diabetes , unknown , and missing ) were excluded ( n = 3 ) . youth were asked to participate in a research visit and they and/or their parent provided written informed consent according to the guidelines established by the nnhrrb . information about dietary intake , physical activity , smoking , and depressive symptoms was collected from participants aged 10 years . diet was assessed by a food frequency questionnaire modified for administration in youth and capturing culturally specific foods ( 10 ) . physical activity questions were from the youth risk behavioral surveillance system questionnaire ( 11 ) . depressive symptoms were assessed using the center for epidemiologic studies  depression scale ( ces - d ) ( 12 ) . a ces - d score 24 was used as evidence of severely depressed mood ( 13 ) . blood was drawn after an overnight fast under conditions of metabolic stability ( 14 ) for measurement of gad65 antibodies and fasting and stimulated c - peptide ( mixed - meal challenge ) , which were used to further characterize the provider - assigned diabetes type . a1c , fasting glucose , and lipids ( total and hdl and ldl cholesterol , triglycerides , apolipoprotein b , and ldl particle density ) were also measured ( 9 ) . glycemic control was categorized according to american diabetes association guidelines ( 15 ) as adequate when a1c < 8% and poor when a1c 9.5% . a spot - urine sample was collected in the morning , and urinary albumin and creatinine were measured . an albumin - to - creatinine ratio for youth aged 3 years , a physical examination included height , weight , and waist circumference ; evaluation for acanthosis nigricans ; and measurement of systolic and diastolic blood pressure ( 9 ) . obesity was defined as a bmi 95th percentile , and overweight was a bmi in the 85th to < 95th percentile ( 17 ) . weight and height were compared with u.s . waist circumference was measured using the national health and nutrition examination survey protocol ( 17 ) . elevated blood pressure levels were present if systolic or diastolic blood pressure were 95th percentile for age , sex , and height . hypertension was estimated based on elevated blood pressure levels or antihypertensive medication use ( 18 ) . comparisons were made between subgroups of diabetes types ( type 1 and type 2 diabetes ) to determine whether characteristics differed . linear or logistic regression was used to adjust for differences in age and duration of diabetes between type 1 and type 2 diabetic patients . given the descriptive nature of these analyses , we used an  level of 0.05 and did not correct for multiple comparisons . the search - navajo study sought to identify all prevalent cases of diabetes in 2001 and all incident cases in 20022005 . the study was approved by the indian health services ( ihs ) directors , directors of tribally operated health care facilities , and the navajo nation human research review board ( nnhrrb ) and was health insurance portability and accountability act compliant . the population denominator was defined as individuals aged < 20 years who self - identified themselves as navajo and had at least one visit in the preceding 3 years to an eligible health care facility . health care facilities include six navajo area his units ( chinle , crownpoint , fort defiance , gallup , kayenta , and shiprock ) and two tribally operated facilities ( tuba city and winslow ) . potential case subjects had one or more outpatient visits or hospitalizations coded for diabetes ( icd-9 codes 250.0250.9 ) and were aged < 20 years on 31 december 2001 . for 20022005 incidence estimates , the denominator included eligible youth with at least one visit in the preceding 3 calendar years . the sum of the annual denominators was used as average total denominator ( n = 380,633 person - years ) over the 4-year period . potential case subjects had one or more diabetes - related icd-9 codes , were diagnosed in 20022005 , and were aged < 20 years on 31 december of the year of diagnosis . less than 50% of case subjects identified using the ihs database had diabetes ; miscoding was the most common reason for invalid case reports . for all validated cases , core demographic and diagnostic information was obtained from medical records . the clinical diabetes type assigned by the health care provider was categorized as type 1 ( combining types 1 , 1a , and 1b ) and type 2 diabetes . youth with other types ( including hybrid , secondary diabetes , unknown , and missing ) were excluded ( n = 3 ) . youth were asked to participate in a research visit and they and/or their parent provided written informed consent according to the guidelines established by the nnhrrb . information about dietary intake , physical activity , smoking , and depressive symptoms was collected from participants aged 10 years . diet was assessed by a food frequency questionnaire modified for administration in youth and capturing culturally specific foods ( 10 ) . physical activity questions were from the youth risk behavioral surveillance system questionnaire ( 11 ) . depressive symptoms were assessed using the center for epidemiologic studies  depression scale ( ces - d ) ( 12 ) . a ces - d score 24 was used as evidence of severely depressed mood ( 13 ) . blood was drawn after an overnight fast under conditions of metabolic stability ( 14 ) for measurement of gad65 antibodies and fasting and stimulated c - peptide ( mixed - meal challenge ) , which were used to further characterize the provider - assigned diabetes type . a1c , fasting glucose , and lipids ( total and hdl and ldl cholesterol , triglycerides , apolipoprotein b , and ldl particle density ) were also measured ( 9 ) . glycemic control was categorized according to american diabetes association guidelines ( 15 ) as adequate when a1c < 8% and poor when a1c 9.5% . a spot - urine sample was collected in the morning , and urinary albumin and creatinine were measured . an albumin - to - creatinine ratio 30 g / mg ( 16 ) was considered elevated . for youth aged 3 years , a physical examination included height , weight , and waist circumference ; evaluation for acanthosis nigricans ; and measurement of systolic and diastolic blood pressure ( 9 ) . obesity was defined as a bmi 95th percentile , and overweight was a bmi in the 85th to < 95th percentile ( 17 ) . waist circumference was measured using the national health and nutrition examination survey protocol ( 17 ) . elevated blood pressure levels were present if systolic or diastolic blood pressure were 95th percentile for age , sex , and height . hypertension was estimated based on elevated blood pressure levels or antihypertensive medication use ( 18 ) . comparisons were made between subgroups of diabetes types ( type 1 and type 2 diabetes ) to determine whether characteristics differed . linear or logistic regression was used to adjust for differences in age and duration of diabetes between type 1 and type 2 diabetic patients . variables that were not normally distributed were logarithmically transformed . given the descriptive nature of these analyses , we used an  level of 0.05 and did not correct for multiple comparisons . table 1 shows the number of navajo youth with prevalent ( 2001 ) and incident diabetes ( 20022005 ) , prevalence and incidence rates , and their distribution by age - group . a total of 92 youth aged < 20 years had diabetes in 2001 , and 66 were newly diagnosed in 20022005 . the prevalence of diabetes in navajo youth was low under the age of 10 years ( 0.11 per 1,000 ) and high ( 2.78 per 1,000 ) in youth aged 1519 years . similarly , the incidence of diabetes was low in children aged < 10 years ( 2.24 per 100,000 per year ) but high in adolescents aged 1519 years ( 39.34 per 100,000 per year ) . overall , 18 prevalent case subjects had type 1 ( 19.6% ) and 74 had type 2 ( 80.4% ) diabetes . there were 10 type 1 ( 15.2% ) and 56 type 2 ( 84.8% ) diabetic patients incident in 20022005 . figure 1 shows type - specific estimates of prevalence ( upper panel ) and incidence ( lower panel ) , according to age - group and sex . estimates of type 1 diabetes prevalence and incidence are low and vary little with age and sex . these data indicate that type 1 diabetes is present in all age - groups and both sexes but is a rare condition among navajo children and adolescents . in contrast , type 2 diabetes is exceptionally rare in youth aged < 10 years ( only one individual with type 2 diabetes ) but very common in adolescents aged 1519 years . among adolescents aged 1519 years in the same age - group , the incidence rates of type 2 diabetes were 38.16 and 32.42 per 100,000 per year in female and male subjects , respectively . incidence rates of type 2 diabetes increased with age ( p = 0.04 for youth aged 1519 years vs. youth aged 1014 years ) and female subjects aged 1014 years were more likely to have type 2 diabetes than male subjects ( p = 0.04 ) . table 2 presents characteristics associated with provider - defined diabetes type . of 158 registered patients , youth with type 2 diabetes were older and had a shorter duration of diabetes than those with type 1 diabetes . almost 50% of youth with clinical type 1 diabetes had positive gad65 antibody titers , while only 20% of those with type 2 diabetes had such antibodies ( p = 0.05 ) . mean fasting and stimulated c - peptide levels were significantly higher in youth with type 2 diabetes , even after adjusting for differences in age and diabetes duration , reflecting important differences in residual insulin secretory capacity and likely different pathophysiologic mechanisms in youth with type 2 versus type 1 diabetes . as expected , youth with type 2 diabetes had significantly higher bmi ( 33.6 vs. 23.5 kg / m ) and bmi z scores ( 1.8 vs. 0.7 ) , as well as higher prevalence of obesity ( 67.7 vs. 12.5% ) . more youth with type 2 diabetes had evidence of insulin resistance , as manifested by presence of acanthosis nigricans ( 64.1 vs. 17.7% ) , than youth with type 1 diabetes . youth with both type 2 and type 1 diabetes had a very strong family history of diabetes ( 92.2 and 76.5% , respectively ) . the presence of diabetic ketoacidosis at diabetes onset was nonsignificantly greater among youth with type 1 diabetes ( 40 vs. 14.3% in type 2 diabetes ) , suggesting a more acute onset possibly caused by more aggressive etiopathogenesis . while all but one youth with type 1 diabetes were on insulin therapy at study visit , only 26.4% of those with type 2 diabetes were treated with insulin ( nine patients with insulin only and another five with insulin and metformin ) . most patients with type 2 diabetes were treated with metformin ( overall 67.9% ) ; however , 15.1% had no pharmacologic treatment for diabetes ( on average 3.5 years after diagnosis ) . no major differences between type 1 and type 2 diabetes youth were noted in terms of glycemic control , health - related behaviors ( smoking , physical activity , total fat , and fruit and vegetable intake ) and socioeconomic status ( family income and education ) . nevertheless , navajo youth with both diabetes types were very likely to have poor glycemic control ( 53.3 and 43.3% of youth with type 1 and type 2 diabetes , respectively , had a1c levels 9.5% ) and a high prevalence of unhealthy behaviors ( smoking , physical inactivity , and high dietary fat ) . in addition , 14.3% of type 1 and 21.9% of type 2 diabetic youth had evidence of severely depressed mood . youth with type 2 diabetes had more metabolic factors associated with obesity and insulin resistance ( higher abdominal fat deposition , dyslipidemia [ higher triglycerides , low hdl cholesterol , and more small dense ldl cholesterol particles ] , and higher albumin - to - creatinine ratio ) . although mean blood pressure levels and the prevalence of elevated blood pressure were similar in type 1 and type 2 diabetes , more patients with type 2 diabetes were on antihypertensive medication ( ace inhibitors ) , resulting in a nonsignificantly higher prevalence of hypertension ( 35.3 vs. 12.5% ; p = 0.1 ) . the search - navajo study is the first population - based study to provide estimates of diabetes prevalence and incidence among navajo youth . we found that diabetes was infrequent in youth aged < 10 years ; however , both prevalence and incidence of diabetes were high in older youth , especially adolescents aged 1519 years . in this age - group , 1 in 359 navajo youth had diabetes in 2001 and 1 in 2,542 developed diabetes annually the majority of diabetes among navajo youth was type 2 diabetes , although type 1 ( autoimmune ) diabetes was present , especially among younger children . of all racial / ethnic groups in the search study , navajo youth aged 1519 years had the greatest risk of type 2 diabetes ( 14 ) . in contrast , the rates of type 1 diabetes in navajo youth were the lowest of all search study racial / ethnic groups ( 14 ) . there are virtually no data on diabetes incidence , and no differentiation according to diabetes type was published . an earlier study ( 7 ) of 160 navajo youth aged 1219 years found that the prevalence of impaired glucose tolerance or undiagnosed diabetes was 8% . in 1999 , kim et al . one student was found to have diabetes ( 0.4% ) and 3% had impaired glucose tolerance or impaired fasting glucose . recent efforts by navajo area ihs investigators are focused on a more comprehensive assessment of the current burden of diabetes in navajo youth ( c.a . , personal communication ) . the majority of data on diabetes among american indian youth come from population - screening studies , such as the pima indian study ( 1 ) . the prevalence of type 2 diabetes among pima indians of arizona is much higher than reported here for navajo youth ( 37.8 and 53.1 per 1,000 among pima male and female subjects aged 1519 years , respectively , vs. 2.07 and 2.63 per 1,000 in navajo male and female subjects aged 1519 years , respectively ) . similarly , the incidence rates of type 2 diabetes are > 10-fold higher among pima youth aged 514 years ( 331.9 per 100,000 per year ) than among navajo youth ( 19 ) . these data may reflect population differences in risk for type 2 diabetes but are also partly due to systematic screening for case ascertainment among the pima indians . using the ihs database , acton et al . ( 20 ) recently found that the prevalence of all diabetes among american indian / alaska native youth aged 1519 years was 5.4 per 1,000 , a figure much closer to that reported here ( 2.78 per 1,000 ) , although this study did not conduct case validation through medical record abstraction . our experience is that 50% of cases identified through the navajo ihs database in youth aged < 20 years were not valid diagnoses of diabetes , due largely to miscoding . another recent study ( 21 ) conducted between 1999 and 2001 among american indian youth aged < 20 years in montana and wyoming used methods similar to the search study ( case identification through the ihs database followed by medical record validation ) . in these populations , the prevalence and incidence of diabetes were similar to those reported for navajo indians ( prevalence estimates were 0.7 and 1.3 per 1,000 and incidence rates were 5.8 and 23.3 per 100,000 per year for type 1 and type 2 diabetes , respectively ) . our study also provides important descriptive information on characteristics of diabetes type , as well as risk factors for chronic complications . in addition , there was a high prevalence of obesity and related cardiometabolic disturbances ( central fat deposition , dyslipidemia , and hypertension ) , especially among type 2 diabetic youth ( table 3 ) . no such information was previously available in youth with diabetes , although one of the earliest studies ( 6 ) of nondiabetic navajo youth found them to have higher bmi levels , with higher triglyceride and lower hdl cholesterol levels than nhw youth . coupled with high prevalence of unhealthy behaviors ( smoking , high - fat diets , and sedentary lifestyles ) and lower socioeconomic status ( table 3 ) , these findings may translate to an increased prevalence of cardiovascular disease in the future as these youth mature . because the ihs facilities provide universal health care coverage to all american indian / alaskan native people , we do not believe that our ascertainment approach excluded an important number of youth with diabetes . we may , therefore , have underestimated the true risk of type 2 diabetes in navajo youth . similar to other population - based studies ( 1,22 ) , our analyses utilized diabetes type assignments made by health care providers . diabetes type was further characterized in a subset of navajo youth participating in the research visit . with a clinical diagnosis of type 1 diabetes , gad65 antibody positivity was present in almost 50% of individuals ( table 2 ) , similar to other racial / ethnic groups participating in the search study ( 14 ) . the gad65-negative participants with type 1 diabetes may have lost gad positivity , may be positive for other autoantibodies , or may have other causes of insulin deficiency . with a clinical diagnosis of type 2 diabetes , 20.3% of navajo participants had positive gad65 antibodies , which is similar to other racial / ethnic groups participating in the search study ( 14 ) , as well as other smaller u.s . studies ( 23 ) . the role of autoantibody positivity in the etiology and natural evolution of diabetes among youth with a clinical phenotype of type 2 diabetes requires further exploration . our data provide strong evidence that diabetes is an important health problem for navajo youth . because young people with diabetes will have more years of disease burden and an increased risk of developing diabetes - related complications early in life , targeted efforts aimed at primary prevention of diabetes in navajo youth and efforts to prevent or delay the development of chronic complications among those who already developed diabetes are warranted .
objective  to estimate the prevalence and incidence of diabetes , clinical characteristics , and risk factors for chronic complications among navajo youth , using data collected by the search for diabetes in youth study ( search study).research design and methods  the search study identified all prevalent cases of diabetes in 2001 and all incident cases in 20022005 among navajo youth . 
 we estimated denominators with the user population for eligible health care facilities . 
 youth with diabetes also attended a research visit that included questionnaires , physical examination , blood and urine collection , and extended medical record abstraction.resultsdiabetes is infrequent among navajo youth aged < 10 years . 
 however , 
 both prevalence and incidence of diabetes are high in older youth . among adolescents aged 1519 years , 1 in 359 navajo youth had diabetes in 2001 and 1 in 2,542 developed diabetes annually . 
 the vast majority of diabetes among navajo youth with diabetes is type 2 , although type 1 diabetes is also present , especially among younger children . 
 navajo youth with either diabetes type were likely to have poor glycemic control , high prevalence of unhealthy behaviors , and evidence of severely depressed mood . 
 youth with type 2 diabetes had more metabolic factors associated with obesity and insulin resistance ( abdominal fat deposition , dyslipidemia , and higher albumin - to - creatinine ratio ) than youth with type 1 diabetes.conclusionsour data provide evidence that diabetes is an important health problem for navajo youth . targeted efforts aimed at primary prevention of diabetes in navajo youth and efforts to prevent or delay the development of chronic complications among those with diabetes are warranted 
 .