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Prevalence of Diabetes in U.S. Adults from 1988-2012

Overall prevalence of diabetes may have increased, but undiagnosed diabetes may be declining.

Previous studies have shown that type 1, diagnosed and undiagnosed diabetes have increased in the population of the United States in past decades. Supporting these findings, diagnosed diabetes between the years of 1990 and 2008 increased from 3.5% to 7.9% before leveling off between 2008 and 2012. The prevalence of prediabetes rose between the years 1999-2010. These increases seem to mirror the trend of increasing obesity, an important risk factor for type 2 diabetes. New data has recently become available to estimate the prevalence and trends of total diabetes in the U.S. population.

The current study was accomplished using a cross-sectional analysis of surveys conducted between the years 1988-1994 and 1999-2012. The National Health and Nutrition Examination Survey (NHANES) was used to estimate the prevalence of total diabetes (undiagnosed + diagnosed), undiagnosed diabetes, and diagnosed diabetes in adults of the U.S. A total of 2,781 adults from 2011-2012 and 23,634 from 1988-2010 were surveyed to estimate the trends in question.

A participant was considered to have diabetes if they had a previous diagnosis, or if there was no previous diagnosis, but they had an HbA1c of 6.5% or greater, a fasting plasma glucose (FPG) of 126 mg/dL or greater, or a 2-hour plasma glucose (2-hour PG) level of 200 mg/dl or greater. A participant was considered to have prediabetes if they had an HbA1c of 5.7% to 6.4%, and FPG of 100 mg/dL to 125 mg/dL, or a 2-hour PG of 140 mg/dL to 199 mg/dL.

Participants filled out a standard questionnaire reporting sex, age, ethnicity, income level and education level. They were also asked if they had been diagnosed with diabetes by a doctor or healthcare professional. During an examination, weight and height were measured to calculate BMI, as well as blood taken to calculate HbA1c and FPG. The 2-hour PG was accomplished by using a 75-gram dose of glucose and a venipuncture 2 hours later.

The unadjusted prevalence of total diabetes from 2011-2012 was 14.3%, CI: 12.2% to 16.8%, diagnosed diabetes: 9.1%, CI: 7.8% to 10.6%, undiagnosed diabetes: 5.2%, CI: 4.0% to 6.9%, and prediabetes: 38%, CI: 12.2% to 16.8%. 36.4% of the participants with diabetes were undiagnosed. The age-standardized prevalence of total diabetes in white participants: 11.3%, CI 9.0% to 14.1%, non-Hispanic blacks: 21.8%, CI 17.7% to 26.7%, non-Hispanic Asians: 20.6%, CI: 15.0% to 27.6%, and Hispanics: 22.6%, CI: 18.4% to 27.5%. Furthermore, the age-standardized undiagnosed was highest in non-Hispanic Asians and Hispanics, 50.9%, CI 38.3% to 63.4% and 49.0%, CI: 40.8% to 57.2% respectively. Total diabetes, when standardized by age, increased from 9.8%, CI 8.9% to 10.6% in 1988-1994 to 10.8%, CI: 9.5% to 12.0% in 2001-2001, to 12.4%, CI: 10.8% to 14.2% in 2011-2012.

Before drawing any conclusions, it should be noted that a participant’s previous diabetes diagnosis was determined based upon self-reporting only. Also, the American Diabetes Association (ADA) recommends repeating a measurement of HbA1c, FPG or 2-hour PG to diagnose diabetes. This was not possible as most participants had only 1 NHANES study visit, which means some participants may have been classified as diabetic without actually having diabetes as defined by the ADA. Bearing that in mind, this study suggests that the prevalence of diabetes in U.S. adults increased between 1990 and 2008, with a plateau between 2008 and 2012.

Over the same time period, the proportion of people with undiagnosed diabetes has significantly decreased, with the exception of Mexican-American participants, in which it increased. It is likely that the decrease in undiagnosed diabetes is due to better screening and longer survival rates of diabetics. These improvements may not be seen in young Hispanic individuals as a result of a lack of health insurance and consequently, less access to healthcare.

Practice Pearls:

  • In 2011-2012 the estimated prevalence of diabetes in U.S. adults was 12.4%.
  • The highest percentage of adults with diabetes occurred in non-Hispanic blacks, non-Hispanic Asians, and Hispanics.
  • Between 1988-1994 and 2011-2012, the prevalence of diabetes in U.S. adults increased from 9.8% to 12.4%.

Researched and prepared by Devon Brooks, Doctor of Pharmacy Candidate from LECOM College of Pharmacy, reviewed by Dave Joffe, BSPharm, CDE

 

Menke A, Casagrande S, Geiss L, Et al. “Prevalence of the trends in diabetes among adults in the United States, 1988-2012.” JAMA. (2015) 314(10):1021-1029.