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Research Letter
November 14, 2017

Change in Testing, Awareness of Hemoglobin A1c Result, and Glycemic Control in US Adults, 2007-2014

Author Affiliations
  • 1Heller School of Social Policy and Management, Brandeis University, Waltham, Massachusetts
  • 2Division of Endocrinology, Tufts Medical Center, Boston, Massachusetts
  • 3Department of Computer Science, Iowa State University, Ames
  • 4Predictive Analytics and Comparative Effectiveness Center, Tufts Medical Center, Boston, Massachusetts
JAMA. 2017;318(18):1825-1827. doi:10.1001/jama.2017.11927

In 2014, an estimated 30.3 million people (9.4%) in the United States had diabetes.1 Improving glycemic control reduces the risk of diabetes-related vascular complications.2 Studies have shown improvement in glycemic control in the United States from 1998 through 2010, as measured by hemoglobin A1c (HbA1c).3,4 We examined recent trends in glycemic control and patient awareness of HbA1c test results and targets.

Methods

The study was exempted from review by the institutional review board at Tufts Medical Center. We used data from 4 survey periods of the National Health and Nutrition Examination Survey (NHANES; survey periods: 2007-2008, 2009-2010, 2011-2012, and 2013-2014), a representative sample of the US noninstitutionalized population with average response rates of 75.4% for the study period.5 A subsample of surveyed participants was asked to complete laboratory tests and physical examinations. Respondents 20 years and older who reported having diabetes diagnosed by a clinician were included in this analysis.

We calculated the proportion of survey participants with an HbA1c level less than 7% (good control), less than 8% (moderate control), and greater than 9% (poor control). We also calculated the proportion of participants who reported having a test for HbA1c in the prior year and who were aware of their HbA1c result and their target HbA1c level. We analyzed results by subgroups of age (20-44, 45-65, and >65 years), race (white vs nonwhite), and sex. Survey weights were used to calculate proportions. P values for trend over the 4 survey periods were calculated using a multilevel logistic regression in STATA (StataCorp), version 14. Age, sex, body mass index, race, insurance status, education, and income3 were included as covariates of the first level, and survey period as the dependent variable of the second level. No covariates were included for the subgroup trend analyses. Significance was defined as a 2-tailed P value less than .05.

Results

Of 23 482 participants, 2908 (12.40%) reported having diabetes (mean age, 62 years [SD, 12.96]; women, 50.40%; white race, 35.80% [unweighted]). Median HbA1c level was 6.90% (interquartile range [IQR], 6.20%-8.15%) in 2007-2008 and 6.95% (IQR, 6.30%-8.20%) in 2013-2014 (P = .39) (Table 1). Glycemic control did not change between 2007-2008 and 2013-2014 overall or in any subgroup (Table 1). Over time, a higher proportion of patients with diabetes reported having an HbA1c test within the past year; 55.10% (95% CI, 49.69%-60.50%) in 2007-2008 to 77.78% (95% CI, 75.07%-80.48%) in 2013-2014 (P value for trend <.001) (Table 2). All subgroups showed a similar change. In 2007-2008, 52.32% (95% CI, 47.63%-57.00%) of patients reported being aware of their past year HbA1c result. This proportion increased to 74.31% (95% CI, 69.63%-78.99%) in the 2013-2014 survey (P value for trend <.001). The change was statistically significant in all subgroups except participants aged 20 to 44 years (P value for trend = .16). The proportion of participants who were aware of the target HbA1c level set by their clinician increased from 2007-2008 (74.07% [95% CI, 70.48%-77.66%]) to 2013-2014 (89.70% [95% CI, 86.11%-93.29%]) (P value for trend <.001). The change was statistically significant in all subgroups except participants aged 20 to 44 years (P value for trend = .81) (Table 2).

Table 1.  
Hemoglobin A1c (HbA1c) Levels in Participants Reported as Having Diabetes (NHANES 2007-2008 Through 2013-2014)a
Hemoglobin A1c (HbA1c) Levels in Participants Reported as Having Diabetes (NHANES 2007-2008 Through 2013-2014)a
Table 2.  
Hemoglobin A1c (HbA1c) Testing and Awareness of Test Results and Targets Among Participants Reporting Diabetesa
Hemoglobin A1c (HbA1c) Testing and Awareness of Test Results and Targets Among Participants Reporting Diabetesa
Discussion

The improvement in glycemic control between 1998 and 2010 among patients with diabetes3 appears to have plateaued during 2007-2014. Approximately 1 in 7 patients with diabetes had poor glycemic control (ie, HbA1c level >9%) throughout the study period despite an increase in the frequency of self-reported HbA1c testing and patient awareness of HbA1c result and patient-specific targets. One potential explanation is that in 2012 the American Diabetes Association set a higher target HbA1c level (8%) for people who are older, frail, and have many comorbidities or diabetes complications6; however, no change in glycemic control was found in the elderly subgroup in this study. Individualization of the target HbA1c level may explain the improvement in HbA1c testing and awareness of HbA1c targets over time in all subgroups except for patients younger than 45 years. Therefore, focusing attention on this subgroup may be important especially because they would benefit most from treatment. Limitations of this study included the cross-sectional study design; therefore, inferences should be made cautiously.

Section Editor: Jody W. Zylke, MD, Deputy Editor.
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Article Information

Accepted for Publication: August 7, 2016.

Corresponding Author: Saeid Shahraz, MD, PhD, Heller School of Social Policy and Management, Brandeis University, 415 South St, Waltham, MA 02453 (shaharz@brandeis.edu).

Author Contributions: Dr Shahraz and Mr Saadati had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Shahraz, Pittas.

Acquisition, analysis, or interpretation of data: Shahraz, Saadati, Thomas, Lundquist, Kent.

Drafting of the manuscript: Shahraz, Lundquist.

Critical revision of the manuscript for important intellectual content: Shahraz, Pittas, Saadati, Thomas, Kent.

Statistical analysis: Shahraz, Saadati.

Administrative, technical, or material support: Thomas, Lundquist, Kent.

Supervision: Pittas, Kent.

Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.

Funding/Support: This study was supported in part by research grants DK076092 and DK098245 from the National Institute of Diabetes and Digestive and Kidney Diseases and the National Institutes of Health Office of Dietary Supplements (Dr Pittas). The study was also partially funded through the Dissemination and Implementation Award (grant DI-1604-35234) from the Patient-Centered Outcomes Research Institute (Dr Kent).

Role of the Funder/Sponsor: The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.

References
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Centers for Disease Control and Prevention.  National Diabetes Statistics Report, 2017: estimates of diabetes and its burden in the united states. https://www.cdc.gov/diabetes/pdfs/data/statistics/national-diabetes-statistics-report.pdf. Accessed August 4, 2017.
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Nathan  DM, Genuth  S, Lachin  J,  et al; Diabetes Control and Complications Trial Research Group.  The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus.  N Engl J Med. 1993;329(14):977-986.PubMedGoogle ScholarCrossref
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Hoerger  TJ, Segel  JE, Gregg  EW, Saaddine  JB.  Is glycemic control improving in US adults?  Diabetes Care. 2008;31(1):81-86.PubMedGoogle ScholarCrossref
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Stark Casagrande  S, Fradkin  JE, Saydah  SH, Rust  KF, Cowie  CC.  The prevalence of meeting A1C, blood pressure, and LDL goals among people with diabetes, 1988-2010.  Diabetes Care. 2013;36(8):2271-2279.PubMedGoogle ScholarCrossref
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Centers for Disease Control and Prevention.  National Health and Nutrition Examination: survey methods and analytic guidelines. https://wwwn.cdc.gov/nchs/nhanes/analyticguidelines.aspx. Accessed January 20, 2017.
6.
American Diabetes Association.  Standards of medical care in diabetes—2012. 2012;35 (suppl 1)S11-S63. PubMed
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