Prevalence of Diagnosed Diabetes in Adults by Diabetes Type — United States, 2016

Kai McKeever Bullard, PhD; Catherine C. Cowie, PhD; Sarah E. Lessem, PhD; Sharon H. Saydah, PhD; Andy Menke, PhD; Linda S. Geiss, MA; Trevor J. Orchard, MD; Deborah B. Rolka, MS; Giuseppina Imperatore, MD, PhD

Disclosures

Morbidity and Mortality Weekly Report. 2018;67(12):359-361. 

In This Article

Abstract and Introduction

Introduction

Currently 23 million U.S. adults have been diagnosed with diabetes.[1] The two most common forms of diabetes are type 1 and type 2. Type 1 diabetes results from the autoimmune destruction of the pancreas's beta cells, which produce insulin. Persons with type 1 diabetes require insulin for survival; insulin may be given as a daily shot or continuously with an insulin pump.[2] Type 2 diabetes is mainly caused by a combination of insulin resistance and relative insulin deficiency.[3] A small proportion of diabetes cases might be types other than type 1 or type 2, such as maturity-onset diabetes of the young or latent autoimmune diabetes in adults.[3] Although the majority of prevalent cases of type 1 and type 2 diabetes are in adults, national data on the prevalence of type 1 and type 2 in the U.S. adult population are sparse, in part because of the previous difficulty in classifying diabetes by type in surveys.[2,4,5] In 2016, supplemental questions to help distinguish diabetes type were added to the National Health Interview Survey (NHIS).[6] This study used NHIS data from 2016 to estimate the prevalence of diagnosed diabetes among adults by primary type. Overall, based on self-reported type and current insulin use, 0.55% of U.S. adults had diagnosed type 1 diabetes, representing 1.3 million adults; 8.6% had diagnosed type 2 diabetes, representing 21.0 million adults. Of all diagnosed cases, 5.8% were type 1 diabetes, and 90.9% were type 2 diabetes; the remaining 3.3% of cases were other types of diabetes. Understanding the prevalence of diagnosed diabetes by type is important for monitoring trends, planning public health responses, assessing the burden of disease for education and management programs, and prioritizing national plans for future type-specific health services.

NHIS is an annual, cross-sectional household interview survey conducted by CDC that gathers health-related data in a nationally representative sample of the civilian, noninstitutionalized U.S. population.[6] The 2016 NHIS Sample Adult Core consisted of 33,028 adults aged ≥18 years, with a final response rate of 54.3%. Each respondent was randomly selected among all adults aged ≥18 years in each household. During face-to-face interviews, respondents were asked whether a doctor or health care professional had ever told them that they had diabetes, other than during pregnancy. Among those who said they had diabetes, questions were asked regarding age at diagnosis and insulin and oral hypoglycemic medication use. In 2016, respondents were also asked to report whether they had type 1, type 2, or another type of diabetes. Virtually all patients with type 1 diabetes require insulin to survive, and very few persons who use insulin do not report using it.[5] Previous studies have found that self-reported diabetes type alone is not a valid method for classifying diabetes type in surveys because some patients are not aware of their diabetes type.[5,7] Therefore, for this analysis, type 1 diabetes was defined as current insulin use and self-report of type 1 diabetes. Adults who reported having type 1 diabetes but reported not using insulin were classified as having type 2 diabetes, as were persons who reported type 2 diabetes, unknown diabetes type, or who would not report diabetes type. Respondents who reported having another diabetes type were classified as having "other type."

Crude prevalence estimates of diagnosed diabetes by type and 95% confidence intervals (CIs) were calculated for the overall population and by selected sociodemographic characteristics. P values were calculated from chi-squared tests and were considered significant at <0.05. Final survey weights were applied to the data to adjust for various probabilities of selection and household nonresponse. Statistical software was used to account for NHIS's complex sampling design.

A total of 3,519 respondents aged ≥18 years reported having diabetes, including 211 classified as having type 1; 3,210 classified as having type 2 (including 182 who reported having type 1, but not taking insulin; 2,897 who reported having type 2; one who reported an unknown type; and one refusal); and 98 classified as having "other" type. In 2016, the overall crude prevalence of diagnosed diabetes among U.S. adults was 9.44% (95% CI = 9.01–9.88). The prevalences of type 1 diabetes, type 2 diabetes, and other diabetes types were 0.55%, 8.58%, and 0.31%, respectively (Table). The weighted percentages of all diagnosed diabetes cases that were type 1 and type 2 were 5.8% and 90.9%, respectively; the remaining were other types. Based on the weighted NHIS population, the estimated numbers of adults with type 1, type 2, and other diabetes types were 1.3 million, 21.0 million, and 0.8 million, respectively.

Estimated crude prevalence of type 1 diabetes among U.S. adults did not significantly vary by age group (p = 0.54) or education (p = 0.14) (Table). The prevalence of type 1 diabetes was higher among men (0.64%) than among women (0.46%) (p<0.05) and higher among non-Hispanic whites (whites) (0.67%) than among Hispanics (0.22%) (p<0.01). By age group, the prevalence of type 2 diabetes was highest among adults aged ≥65 years and lowest among adults aged 18–29 years (p<0.001), and by race/ethnicity, was higher among non-Hispanic blacks (11.52%) than among non-Hispanic Asians (6.89%), whites (7.99%), and Hispanics (9.07%) (p<0.001) (Table). The prevalence of type 2 diabetes decreased with higher levels of educational attainment (p<0.001).

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