Addressing Literacy and Numeracy to Improve Diabetes Care: Two randomized controlled trials

Kerri Cavanaugh; Kenneth A. Wallston; Tebeb Gebretsadik; Ayumi Shintani; Mary Margaret Huizinga; Dianne Davis; Rebecca Pratt Gregory; Robb Malone; Michael Pignone; Darren DeWalt; Tom A. Elasy; Russell L. Rothman

doi:10.2337/dc09-0563

Original Research

Addressing Literacy and Numeracy to Improve Diabetes Care

Two randomized controlled trials

Kerri Cavanaugh, MD, MHS¹,²,
Kenneth A. Wallston, PHD³,
Tebeb Gebretsadik, MPH⁴,
Ayumi Shintani, PHD, MPH⁴,
Mary Margaret Huizinga, MD, MPH⁵,
Dianne Davis, RD, CDE²,
Rebecca Pratt Gregory, RD, CDE²,
Robb Malone, PHARMD, CDE⁶,⁷,
Michael Pignone, MD, MPH⁶,
Darren DeWalt, MD, MPH⁶,
Tom A. Elasy, MD, MPH²,⁸ and
Russell L. Rothman, MD, MPP²,⁸,⁹

¹Division of Nephrology, Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee;
²Vanderbilt Eskind Diabetes Center, Diabetes Research and Training Center, Vanderbilt University, School of Medicine, Nashville, Tennessee;
³School of Nursing, Vanderbilt University Medical Center, Nashville, Tennessee;
⁴Department of Biostatistics, Vanderbilt University Medical Center, Nashville, Tennessee;
⁵Department of Medicine, Division of General Internal Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland;
⁶Department of Medicine, University of North Carolina, Chapel Hill, North Carolina;
⁷Division of Pharmacy Practice and Experiential Education, UNC Eshelman School of Pharmacy, Chapel Hill, North Carolina;
⁸VA Tennessee Valley Healthcare System, VA Quality Scholars Program, Nashville, Tennessee;
⁹Division of General Medicine and Public Health, Department of Medicine, Vanderbilt University School of Medicine, Nashville, Tennessee.

Corresponding author: Russell L. Rothman, russell.rothman{at}vanderbilt.edu.

Diabetes Care 2009 Dec; 32(12): 2149-2155. https://doi.org/10.2337/dc09-0563

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Figure 1
Study flow diagram.

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Table 1

Baseline patient characteristics by group status and trial site

	VUMC		UNC		Overall
	Control	Intervention	Control	Intervention	Control	Intervention
n	53	52	46	47	99	99
Age (years)	45 (31−59)	49.5 (41−57)	56 (51−60)	53 (48.5−58.5)	53 (40−59.5)	52 (45−59)
Men (%)	38	40	33	34	35	37
African American (%)	21	29	72	57	44	42
Income <$20,000/year (%)	25	33	67	72	45	52
Education ≤12th grade (%)	37	33	61	67	48	49
Private insurance (%)	74	75	26	23	52	51
Type 2 diabetes (%)	74	90^*	100	100	86	95^*
Years of diabetes diagnosis	6 (1−12)	6.5 (2−12.3)	9 (5−14.8)	8 (4.5−16)	8 (3−13)	8 (3−15)
Monitor blood glucose ≤ 1 time/day (%)	25	35	49	39	36	37
Insulin use (%)	60	50	78	70	69	59
Insulin >2 times/day	32 (69)	26 (77)	36 (42)	35 (40)	68 (54)	61 (55)
Adjusts insulin for blood glucose	30 (70)	26 (73)	35 (17)	36 (22)	65 (42)	62 (44)
Adjusts insulin for carbohydrates	30 (43)	26 (31)	34 (0)	35 (0)	64 (20)	61 (13)
Yes, hypoglycemic episodes in the prior month (%)	30	25	0	6	16	16
Previous diabetes education (%)	62	69	76	74	69	71
Tobacco use (%)	21	27	26	28	23	27
BMI (kg/m²)	34.4 (27.2−40.1)	34.4 (30.1−39.1)	35.6 (31.7−41.3)	36.9 (29.9−40.6)	35.5 (30.2−41.3)	35.2 (29.9−40.0)
Systolic blood pressure (mmHg)	138 (126−144)	133 (119−142)	131 (121−150)	142 (126−150)	136 (123−146)	136 (121−146)
Diastolic blood pressure (mmHg)	79 (72−84)	76 (70−85)	72.5 (68−82)	77 (69−84)	76 (69−83)	76 (69.5−84.5)
REALM score [0–66]	65 (62−66)	64 (62−65)	59 (44−65)	54 (39−64)	63 (57−66)	63 (46−65)
REALM score <9th grade level (%)	19	18	54	62	35	39
Diabetes numeracy test score (%)	83 (65−90)	69 (44−84)†	33 (13−51)	33 (13−70)	60 (36−86)	55 (21.5−81)
Self-efficacy: PDSMS (8−40)	24.0 (22.0−27.0)	24.5 (20.3−28.8)	26.0 (23.0−33.0)	24.0 (19.5−30.0)	25.0 (22.0−29.5)	24.0 (20.0−29.0)
Satisfaction: DTSQ (0–36)	27.5 (21.0−32.0)	29.0 (26.0−33.0)	31.5 (26.0−34.8)	30.0 (26.0−32.5)	29.0 (23.3−34.0)	29.5 (26.0−33.0)
A1C (%) baseline	8.6 (7.3−9.7)	8.5 (7.5−10.7)	9.8 (8.5−10.3)	9.2 (8.6−10.9)	9.1 (7.6−10.2)	9.1 (7.8−10.8)

↵Data are %, n (%), or median (interquartile range). *P < 0.05 comparing intervention vs. control by either χ² or Wilcoxon rank-sum tests, as appropriate. DTSQ, Diabetes Treatment Satisfaction Questionnaire; PDSMS, Perceived Diabetes Self-Management Scale.

Table 2

Change in A1C, self-efficacy, and satisfaction by study group from baseline

	VUMC			UNC			Combined
	Intervention	Control	P^*	Intervention	Control	P^*	Intervention	Control	P^*
Change in A1C
Baseline to 3 months	−1.60 (−2.07 to −1.00)^†	−1.00 (−1.81 to −0.40)^†	0.121^‡	−1.40 (−1.75 to −0.75)^†	−0.30 (−1.06 to −0.10)^†	0.014	−1.50 (−1.80 to −1.02)^†	−0.80 (−1.10 to −0.30)^†	0.005^§
Baseline to 6 months	−1.15 (−1.43 to −0.77)^†	−1.20 (−2.22 to −0.70)^†	0.657	−0.75 (−1.40 to −0.20)^†	−0.55 (−1.30 to −0.29)^†	0.732	−1.05 (−1.30 to −0.70)^†	−0.90 (−1.30 to −0.53)^†	1.0
Change in self-efficacy (PDSMS)
Baseline to 6 months	+8.0 (3.0 to 8.5)^†	+4.0 (1.0 to 7.2)^†	0.324	+5.0 (2.0 to 6.0)^†	+1.0 (−1.7 to 2.7)	0.030	+5.0 (3.0 to 7.0)^†	+2.0 (1.0 to 4.0)^†	0.018
Change in satisfaction (DTSQ)
Baseline to 6 months	+2.0 (1.0 to 5.0)^†	+3.0 (2.0 to 6.4)^†	0.584	+2.0 (0.4 to 3.0)^†	+0.5 (0.0 to 1.7)	0.474	+2.0 (1.0 to 3.0)^†	+2.0 (1.0 to 3.0)^†	0.836

Data are median (95% CI).
↵*P value determined by Wilcoxon rank-sum test comparing intervention and control.
↵†P < 0.05 for paired comparison of 3- or 6-month value with baseline value using Wilcoxon signed-rank test.
↵‡P = 0.056 for comparison of intervention vs. control in a repeated-measures model using all available 3- and 6-month data, adjusted for age, sex, race, type of diabetes, income, baseline Diabetes Numeracy Test score, and baseline A1C level, including accounting for physician cluster and examination of an interaction term with time.
↵§P = 0.030 for comparison of intervention vs. control in a repeated-measures model using all available 3- and 6-month data, adjusted for age, sex, race, type of diabetes, income, baseline Diabetes Numeracy Test score, and baseline A1C level, including accounting for physician cluster and examination of an interaction term with time. DTSQ, Diabetes Treatment Satisfaction Questionnaire; PDSMS, Perceived Diabetes Self-Management Scale.