Forest plot of mean difference in HbA1c(expressed as percentage) between the digital health intervention and the usual care group, and subgroup analysis by mode of delivery of the intervention (ie, SMS, smartphone application, and website). The size of the squares indicates the weight of the evidence from each of the studies; studies with CI (horizontal line) crossing zero (vertical line) are inconclusive; powerful studies (those with more participants) have narrower CIs; the diamonds represent the summary effect sizes in each of the subgroups and in the overall sample, with the width of the diamond indicating the 95% CI. A statistically greater significant reduction in HbA1cis seen in the digital health intervention group, compared with the control group in the overall sample and with the SMS and smartphone application modes of delivery but not when websites were used as the mode of delivery of the intervention. The data present substantial heterogeneity. HbA1c=glycated haemoglobin A1c.