ST. LOUIS – In addition to problems with health literacy in general, diabetes patients are especially susceptible to problems with a specific aspect of health literacy known as health numeracy.
Numeracy is the ability to understand and use numbers and math skills in daily life. Diabetes requires a lot of health numeracy skills–calculating insulin dosages, counting carbohydrates, calculating ratios for combination insulin regimens, and sick day management, Dr. Russell Rothman said at the annual meeting of the American Association of Diabetes Educators.
Dr. Rothman, director of the Effective Health Communication Program at Vanderbilt University, Nashville, Tenn., and his colleagues tested 398 diabetes patients using a 43-item examination. The patient population was 51% female, and the average age was 54 years; 14% of the patients had type 1 diabetes, and 86% had type 2 diabetes. In terms of education, 43% of the participants had no more than a high school education, and 69% had less than ninth-grade math skills as measured by the Wide Range Achievement Test.
The researchers sought to evaluate patients' ability to count carbohydrates, interpret glucose meter results, apply sliding-scale insulin regimens, calculate insulin dosage based on insulin to carbohydrate intake, and use other diabetes-related numeracy skills. They looked at the relationship between the test score and patients' hemoglobin A1c (HbA1c) levels, and other outcomes.
Patients correctly answered an average of 61% of the test questions. Problem areas included interpreting serving sizes from food labels, using fractions and decimals, and dealing with multiple-step problems (adjusting for blood sugar and carbohydrates at the same time)
Every 10-point increase on the numeracy test translated into an average 0.1% decrease in HbA1c, after adjusting for age, gender, race, income, literacy, insulin status, and type of diabetes. Higher test scores were significantly correlated with higher educational status, literacy, math skills, and frequency of blood glucose monitoring.
Many people aren't good at estimating portion sizes, which causes difficulty when it comes to estimating insulin dosages correctly, said Dr. Rothman. “That brings home the importance of using measuring devices in diabetes education.”