This systematic review and meta-analysis of randomised controlled trials and observational studies found that overall, SDM interventions increased knowledge, informed choice, participation in decision-making, decision self-efficacy, preference for collaborative decision making and reduced decisional conflict among disadvantaged patients.
Further, 7 out of 19 studies compared the intervention’s effect between high and low literacy groups. Overall, shared decision making interventions seemed to benefit disadvantaged groups (e.g. lower literacy) more than those with higher literacy, education and socioeconomic status. Interventions that were tailored to disadvantaged groups’ needs appeared most effective.
The authors report that disparities in knowledge, decisional conflict, uncertainty and treatment preferences between disadvantaged groups and more privileged populations tended to disappear post-intervention use. Disadvantaged groups may therefore benefit from shared decision making interventions more than higher literacy/higher education groups. In the long-term, this may reduce health disparities.
However, two studies suggested that knowledge gain had been affected by patients’ literacy level. This suggests that the intervention’s content was perhaps not sufficiently tailored to disadvantaged groups’ needs, thus limiting the intervention’s impact. The analysis revealed that the layout, use of language, complexity, length and format of the intervention interfered with the intervention’s effect among disadvantaged groups, when there were no significant differences among higher literacy patients. In other words, simple and concise interventions, written in plain language and specifically tailored to disadvantaged groups’ information and decision support needs appeared most beneficial to underprivileged patients.
These interventions had no significant effect on disadvantaged patients’ adherence levels, anxiety, and health outcomes, and no clear effect on screening/treatment preferences, intentions or uptake. This finding is not unique to disadvantaged patients and is consistent with the results of the latest Cochrane review of patient decision aids, which found no clear effect of patient decision aids on adherence, anxiety and condition-specific health outcomes.