Retrospective analyses (21 studies) reported adherence rates that ranged from 31% to 87% (11 studies) and persistence rates (proportion still taking medication) at 12 months that ranged from 16% to 63% (three studies) and at 24 months that ranged from 29% to 70% (two studies). Only one study evaluated insulin in young people with Type 1 diabetes; it reported 28% of participants used less than their prescribed dose. Some studies reported results for the impact of depression and dosing frequency; these were discussed in the review.
Prospective analyses (seven studies) reported adherence to medication when measured using the medication electronic system that ranged from 53 to 98% (five studies). Surveys reported that problems that affected adherence were side effects (one study) and depression (one study).
Intervention trials (eight studies) reported no impact of pharmacist interventions (two studies), behavioural interventions or telephone contact by a nurse diabetes educator (three studies) and cue-dosing (one study). One study reported significant improvements in adherence with mailed medication refill reminders, unit-dose packaging and a combination of these. A survey reported that adherence aids affect glycaemic control.