Table 1. Characteristics of included studies.
| Country | Authors (year) | Year | Sample size | Main aims | Study design | Setting | Tool | Participants | Prevalence: % (n/N) |
|---|---|---|---|---|---|---|---|---|---|
| Brazil | De Castro, S. H., et al (2014) | NR | 150 | To assess the frequency of full and functional health illiteracy | Cross-sectional | Hospital outpatient | s-TOFHLA | Mean age = 58.5 years (SD 9.8), 52.4%, female, 28.4%—less than high school education. | 26.7% (40/150) |
| Brazil | Souza, J. G., et al (2014) | 2012 | 129 |
To investigate the relationship between functional health literacy and glycaemic control in a sample of older patients
|
Cross-sectional | Hospital outpatient | SAHLPA-18 | Mean age = 75.9 years (SD 6.2), 69.8%, female, 82.9%—having less than a high-school diploma. |
56.6% (73/129) |
| Canada | Al Sayah, F., et al (2015) | NR | 154 | To examine the relationship of inadequate health literacy (HL) with changes in depressive symptoms, health-related quality of life and cardiometabolic outcomes in patients recently screened positive for depression. | Longitudinal | Primary care clinics | BHLS |
Mean age = 58.1 years (SD 9.4), 55.8%, female, 13.7%—less than high school | 15.6% (24/154) |
| Canada | Sayah, F. A., et al (2016) | 2013 | 1948 | To examine the association of health literacy (HL) with changes in health-related quality of life (HRQL) |
Longitudinal | Primary care clinics | BHLS | Mean age = 65.6 years (SD 11.4), 45%, female, 14.2%—less than high school education. | 12.5% (244/ 1948) |
| Marshall Island | Bohanny, W. M., et al (2013) | 2009 | 150 | To explore the relationships among health literacy, self-efficacy, and self-care behaviors |
Cross-sectional study | Primary care clinics | s-TOFHLA | Mean age = 52.7 years (SD 10.5), 53.3%, female, 44%—less than high school | 24% (36/150) |
| South Korea | Kim, S. H. (2009) | 2007 | 53 |
To investigate the relationships of health literacy to chronic medical conditions and the functional health status
|
Cross-sectional study | Community based | Korean Functional Health Literacy test | Mean age = 67.2 years, 63.3%, female with limited literacy. |
37.7% (20/53) |
| Switzerland | Franzen, J., et al (2014) | 2011 | 493 | To measure functional HL among persons having type 2 diabetes and to investigate the relationship between functional HL and health care costs and utilization |
Cross-sectional study | Insurer’s database | BHLS | Mean age = 67.5 years, 51.5% belongs to 65-70-year-old group, n = 391, 32.7%, female | 7.3% (36/493) |
| Switzerland | Mantwill, S., et al (2015) | 2012 | 391 | To determine the relationship between health literacy and three years of medication costs | Cross-sectional study | Insurer’s database | BHLS | Mean age = 63.8 years (SD 6.1), 32.2%, female, 13.1%—less than high school education. | 8.7% (34/391) |
| Taiwan | Chen, G. D., et al (2014) | 2012 | 467 |
To demonstrate the interaction of health literacy and understanding of health education and instructions in achieving glycemic control
|
Cross-sectional study | Hospital outpatient | MHLS | Mean age = 68.3 years (SD 7.4), 70.2%, female with limited literacy, 61.5%—less than compulsory education | 47.3% (221/467) |
| Taiwan | Tseng, H.-M., et al (2017) | NR | 232 | To explore the mechanisms through which HL is associated with the health outcome of diabetic care | Cross-sectional study | Hospital outpatient | NVS | Mean age = 58.1 years (SD 9.49), 44.8%, female, 90.1%—secondary education and less |
76.3% (177/232) |
| Netherlands | van der Heide, I., et al (2014) | 2010 | 1676 |
To investigate whether diabetes knowledge can account for part of the relation between health literacy and diabetes self-management behaviour
|
Cross-sectional study | Primary care clinics | BHLS | 65–74 years group (31.7%), 49.6%, female, 44.9% low level of education | 9.8% (164/1676) |
| United States of America (USA) | Schillinger, D., et al (2002) | 2000 | 408 | To examine the association between health literacy and diabetes outcomes | Cross-sectional study | Primary care clinics | s-TOFHLA | Mean age = 62.7 years (SD 10.9), 58%, female, 46%—some high school education or less |
51.5% (210/408) |
| United States of America (USA) | Rothman, R., et al (2004) | 2000 | 111 | To examine the role of literacy in patients with poorly controlled diabetes who were participating in a diabetes management program that included low-literacy-oriented intervention |
Cross-sectional study | Hospital internal medicine clinic | REALM | Mean age = 60 years, 56%, female has limited health literacy, 82%—less than high school education | 55% (61/111) |
| United States of America (USA) | Laramee AS, et al (2007) | 2005 | 998 | To determine the prevalence of limited literacy in diabetic patients with heart failure (HF) compared to those with diabetes and no HF |
Cross-sectional study | Primary care clinics | s-TOFHLA | Mean age = 65 years (22–93), 54%, female, 25%—less than high school graduate. | 17.1% (171/998) |
| United States of America (USA) | DeWalt, D. A., et al (2007) | 2005 | 268 | To examine the relationship between literacy and trust, self-efficacy, and participation in medical decision making |
Cross-sectional study | Hospital outpatient | REALM | Mean age = 62 years (SD 10), 57%, female with limited health literacy . |
19.8% (53/268) |
| United States of America (USA) | Aikens JE, Piette JD. (2009) | 2007 | 1376 |
To determine how patients’ beliefs about antihyperglycemic and antihypertensive medications relate to medication underuse and health status. |
Cross-sectional study | Primary care clinics | BHLS | Mean age = 55.3 years (SD 11.8), 61.6%, female, 21.6%—less than high school | 38.2% (525/1376) |
| United States of America (USA) | Jeppesen KM, et al (2009) | 2007 | 225 | To identify questions that could best indicate to a clinician that a patient may have low or marginal health literacy | Cross-sectional study | Primary care clinics | s-TOFHLA | Mean age = 53.8 years (SD 12.8), 68.4%, female, 44.9%—less than high school education. |
15.1% (34/225) |
| United States of America (USA) | Mancuso, J. M. (2010) | NR | 98 |
To examine if health literacy and patient trust in one’s health-care provider impact glycemic control in an uninsured population
|
Cross-sectional study | Primary care clinics | TOFHLA | Mean age = 52 years (SD 9.1), 60.8%, female, 33.3%—Less than high school education. |
37.8% (37/98) |
| United States of America (USA) | Mbaezue N, et al (2010) | 2005 | 189 | To examine the relationship between health literacy and self-monitoring of blood glucose (SMBG) | Cross-sectional study | Hospital-based clinic | s-TOFHLA | Mean age = 51.2 years (SD 10.0), 58.7%, female, 32.3%—less than high school education. |
39.2% (74/189) |
| United States of America (USA) | Wallace, A. S., et al (2010) | 2008 | 195 |
To examine whether demographic characteristics, insurance status, literacy, duration of diabetes, and intensity of care management were associated with PACIC ratings |
Cross-sectional study | Hospital diabetes clinic | s-TOFHLA | Mean age = 58 years (range: 23–85), 64%, female, 34%—Less than high school education. | 31.3% (61/195) |
| United States of America (USA) | Bauer, A. M., et al (2013) | 2006 | 1366 | To determine whether health literacy limitations are associated with poorer antidepressant medication adherence. | Cohort study | Insurer’s database | BHLS | Mean age = 58.7 years (SD 10.5), 59.9%, female with limited Health literacy, 28.1%—less than high school |
72% (984/1366) |
| United States of America (USA) | Bowen, M. E., et al (2013) | 2009 | 144 | To describe the association among numeracy, total energy, and macronutrient intake |
Cross-sectional study | Primary care clinics | REALM | Median age = 56 years, 53%, female, 26%—high school education or less |
11.1% (16/144) |
| United States of America (USA) | Morris, N. S., et al (2013) | 2007 | 751 | To evaluate the stability of health literacy over time | Longitudinal study | Primary care clinics | s-TOFHLA | 12% belong to 70 years old age group, 53%, female with limited health literacy, 70%—Some high school education. |
12.8% (96/751) |
| United States of America (USA) | Mayberry, L. S., et al (2014) | 2012 | 183 | To assess whether obstructive family behaviors had a stronger relationship with worse glycemic control among patients with limited HL than among those with adequate health literacy |
Cross-sectional study | Hospital outpatient | s-TOFHLA | Mean age = 51.2 years (SD 10.6), 70%, female, 64%—less than high school education | 26.2% (48/183) |
| United States of America (USA) | Thurston, M. M., et al (2015) | 2013 | 192 | To determine (1) if a relationship exists between health literacy and self-reported or objectively measured medication adherence and (2) which aspect or aspects of medication nonadherence are most associated with health literacy |
Cross-sectional study | Primary care clinics | s-TOFHLA | Mean age = 54.4 years (SD 10.3), 56.8%, female, 64.6%—less than high school education | 32.8% (63/192) |
| United States of America (USA) | Sayah, F. A., et al (2015) | 2010 | 343 | To examine the associations between inadequate health literacy and behavioral and cardiometabolic parameters |
Cross-sectional study | Primary care clinics | BHLS | Mean age = 57.4 years (SD 10.11), 68%, female, 25%—less than high school education | 23.9% (82/343) |
| United States of America (USA) | Goonesekera, S. D., et al (2015) | 2012 | 682 | To examine racial/ethnic differences in receipt of hypoglycaemic medications and glycaemic control |
Cross-sectional study | Community based | s-TOFHLA | 56% belongs to less than 65 years old group, 51%, female, 18%—less than high school. | 51.5% (351/682) |
| United States of America (USA) | Fan, J. H., et al (2016) | 2014 | 208 | To investigate the relationship between health literacy and overall medication nonadherence, unintentional nonadherence, and intentional nonadherence |
Cross-sectional study | Primary care clinics | BHLS | Mean age = 53 years (SD10.9), 70.9%, female, 19%—had less than a high school education | 63.5% (132/208) |
| United States of America (USA) | Nelson, L. A., et al (2016) | NR | 80 | To examine the relationship between patient factors and engagement in an mHealth medication adherence promotion intervention for low-income adults | Intervention study | Hospital outpatient | BHLS | Mean age = 50.1 years (SD 10.5), 54%, female, 56.3%—less than a high school degree | 46.3% (37/80) |