SUMMARIES FOR PATIENTS
Association of Numeracy and Diabetes Control
20 May 2008 | Volume 148 Issue 10 | Page I-53
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The summary below is from the full report titled "Association of Numeracy and Diabetes Control." It is in the 20 May issue of Annals of Internal Medicine (volume 148, pages 737-746). The authors are K. Cavanaugh, M.M. Huizinga, K.A. Wallston, T. Gebretsadik, A. Shintani, D. Davis, R. Pratt Gregory, L. Fuchs, R. Malone, A. Cherrington, M. Pignone, D.A. DeWalt, T.A. Elasy, and R.L. Rothman.
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What is the problem and what is known about it so far?
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Diabetes requires the patient to do most of the thinking. One of the most difficult tasks is working with numbers (for example, calculating the number of calories in a portion of food or deciding how much insulin to take after a high blood-sugar test result). People vary in their ability to understand numbers and solve math problems. Moreover, the average blood sugar varies widely among patients with diabetes. Therefore, improving diabetic patients' skills with numbers might improve their diabetes self-care.
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Why did the researchers do this particular study?
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To test diabetic patients' ability to work with numbers and to see whether skill with using numbers is associated with good control of blood sugar.
Patients with diabetes from 2 primary care clinics and 2 clinics that specialized in caring for patients with diabetes. The patient population was 63% white. A total of 43% did not complete high school, and 44% had an annual income less than $20,000.
The authors measured reading ability (literacy) and basic skill with numbers (numeracy) using proven tests used in many research projects. They also developed a test of skill in calculating and interpreting numbers that patients must use in the daily tasks of managing their diabetes (Diabetes Numeracy Test). For example, one question gave the desirable range of blood sugar and asked which of 3 values was in this range. The authors measured the patients' hemoglobin A1c levels, which indicate a patient's average blood sugar.
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What did the researchers find?
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Nearly one third of the patients had reading skills less than a 9th-grade level, and 69% had less than 9th-grade skills with numbers. One half of the patients got a score of 70% or less on the test of diabetes numeracy. One problem stated: "You have a prescription for Metformin 500-mg tablets. The label says ‘Take 1 tablet with supper each night for the first week. Then, increase by 1 tablet each week for a total of 4 tablets daily with supper.’ How many tablets should you take with supper each night the second week?" Only 65% selected the correct answer, which is 2 tablets. Patients who were older, were nonwhite, and had less formal education had lower diabetes numeracy test scores.
At every level of diabetes numeracy, the average blood sugar varied widely from patient to patient. In the entire study sample, lower numeracy was associated with slightly worse blood sugar. This relationship was stronger in certain patients: those who were younger, had worse health-related literacy, or had recently received a diabetes diagnosis.
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What were the limitations of the study?
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Although the patients were diverse in racial origin, income, and education, they all spoke English. The study did not report the frequency of mistakes that led to serious problems, such as dangerously low blood sugar.
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What are the implications of the study?
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Most of these patients were not skilled with numbers (poor diabetes numeracy) and had difficulty with problems that they would need to solve in the everyday management of their diabetes. However, at every level of diabetes-related numeracy—from good to poor—their average blood sugar varied widely. Although the patients' skill with numbers was associated with slightly better blood sugar levels, it appeared to be a small factor in managing their diabetes.
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