Published randomised or quasi-randomised controlled trials of adults that evaluated complex interventions intended to improve health outcomes for people with limited literacy or numeracy were eligible for inclusion. Studies had to measure of at least one of the following outcomes: clinical (health or psychological); health knowledge; health behaviours; self-reported health status/quality of life; self-efficacy/confidence in relation to health/health behaviour; utilisation of health care; and health professional behaviour.
Participants in the eligible studies included those with mixed and limited literacy/numeracy. Interventions were conducted in out-patient settings, community settings, a maternity unit and a hospital pharmacy. Most interventions were health education and related to condition management. Most interventions included between one and 17 contacts. The interventions were compared to any active or inactive control. Controls included usual care, waiting list, alternate complex intervention and attention control or minimal intervention. Health issues studied included newborn hearing screening, hypertension, heart failure, colorectal cancer screening, nutrition education for cancer and cardiovascular disease, medication adherence and understanding, diabetes management, HIV (human immunodeficiency virus) medication and knowledge, and depression. Most studies measured reading rather than literacy; where literacy assessments were undertaken, different measurement tools were used. Most studies were conducted in USA.
Two reviewers independently assessed the studies for inclusion. Discrepancies were resolved through discussion and referral to a third reviewer if necessary.