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A Review Of Variations In Prevalence Of Diagnosed And Undiagnosed Diabetes

Oct 29, 2019
Editor: Steve Freed, R.PH., CDE

Author: Onyi Ibeji, PharmD. Candidate, LECOM School of Pharmacy

What are the consequences of undiagnosed diabetes, and could a timely diagnosis of diabetes improve management and health outcomes?

Diabetes is more common than ever before, and it has grown very rapidly in the United States in the past twenty years. More people are being diagnosed with diabetes and unfortunately, the younger population is also highly affected. The longer patients are exposed to this disease, the greater the risk of its complications which include heart attack, kidney failure, stroke, blindness, and amputation. And as the number of diagnoses and complications increases so also does the cost of treatment increase, which impacts both individuals and the society at large. Diabetes is very complicated and challenging, and educating patients with diabetes is very important to help them manage the condition and avoid unnecessary and expensive complications. Appropriate management of diabetes will help patients stay engaged with their care and improve their quality of life. Despite the importance of diagnosing and treating diabetes, there is a huge population of people who are undiagnosed which translates to a large population with poor control.  This review brings to light the incidence of undiagnosed cases and poor control of diabetes.


The majority of the information used in this review was data collected from the National Health and Nutrition Examination Survey (NHANES). A1C, fasting plasma glucose (FPG) and 2-h plasma glucose (2-h PG) were the three markers used to assess diabetes. Between 2011-2014, A1C or FPG was used to indicate that 21.6 million adults were diagnosed with diabetes while 6.6 million were undiagnosed. Using a combination of all three assessment criteria (A1C, FPG and 2-h PG), revealed a total of 33 million cases of diabetes. Undiagnosed diabetes or prediabetes is associated with comorbidities seen in patients with diabetes, and this risk is much higher in this population when compared with people with normal glucose levels. In 2009-2014, the NHANES data  used the A1C/FPG/2-h PG metrics to show the prevalence of the following comorbidities in undiagnosed diabetes and prediabetes cases, in comparison with patients with diabetes and people with normal glucose levels: Overweight among adults greater than 20 years was 86.4% and this was similar to the weight of patients with diabetes at 89.0%; prediabetes was 75.7% and people with normal glucose levels 60.7%. For hypertension, undiagnosed diabetes was 51.1% vs diagnosed diabetes at 58.8%, and prediabetes 34.2% vs normal glucose levels 23.8%. Other comorbidities like high waist circumference, hyperlipidemia, low HDL, and high triglycerides had similar prevalence progression. These data show that complications could exist in undiagnosed diabetes cases and therefore it is important to detect diabetes early and start both treatment of diabetes and associated risk factors on time to prevent and delay these complications.

There are several variations in the prevalence of undiagnosed diabetes by demographic factors. Using A1C/FPG/2-h PG metrics as a proportion of age, the percentage of undiagnosed diabetes showed the highest in individuals aged 20-44 years (41.5%), it was lesser in individuals aged 45-64 (32.7%) and 65-74 years (28.0%)  but it was 40.4% in those greater than or equal to 75 years of age. Unfortunately, there are many missed opportunities for early intervention in younger people due to undetected diabetes. No difference was seen in terms of sex in the prevalence of diagnosed and undiagnosed diabetes. Variations were noticed by race/ethnicity; non-Hispanic Asians (9.3%), Hispanics (8.4%), Mexican Americans (7.8%), non-Hispanic blacks (6.0%), and non-Hispanic whites (4.0%).

Predictors of undiagnosed diabetes were evaluated, and a multivariable assessment detected that a family history of diabetes is related to about 50% decrease in the odds of having undiagnosed diabetes (odds ratio [OR] 0.48, 95% CI 0.33– 0.70). Hospitalization in the past year was associated with a one-third reduction in undiagnosed diabetes (OR 0.66, 95% CI 0.44–0.99). No health care encounter in the past year was associated with an almost six-fold increase in the odds of undiagnosed diabetes (OR 5.85, 95% CI 2.39–14.34).

Despite the improvements in A1C, blood pressure, and lipid levels control, there are major gaps in diabetes control. In people with both type 1 and type 2 diabetes; the older individuals are meeting their A1C and LDL goals while the younger ones less frequently meet their goals. Diabetes education is key to the day to day management of diabetes and poor education or lack of education can lead to unnecessary and expensive complications. It also makes it difficult for people with diabetes to be in control of their health which could thereby decrease their quality of life.

In summary, the incidence of both undiagnosed and diagnosed diabetes increases with age, and the proportion of total diabetes that is undiagnosed is highest in individuals 20-44 years of age and highest in non-Hispanic Asians, all Hispanics, and Mexican Americans when defined by A1C, FPG or 2-h PG criteria. The occurrence of diagnosed diabetes is growing, while undiagnosed diabetes has been constant in the past two decades.  Adding 2-h PG to the metrics detects more undiagnosed diabetes than when only A1C and FPG are used.

Practice Pearls:

  • Despite the improvements in the control and management of complications of diabetes, there are major gaps in diabetes control.
  • Adequately educating patients with diabetes is key to the management of diabetes.
  • The prevalence of undiagnosed diabetes is high and leaving this factor uncontrolled can lead to further complications.

Catherine C. Cowie. “Diabetes Diagnosis and Control: Missed Opportunities to Improve Health” Diabetes Care 2019;42:994–1004 | https://doi.org/10.2337/dci18-0047

Onyi Ibeji, PharmD. Candidate, LECOM School of Pharmacy