Factors associated with adherence to allocated treatment in the ASCEND trial: a mail-based randomised trial of aspirin and of omega-3 fatty acid supplementation in people with diabetes.

Overall adherence rates were 47.2% for aspirin/placebo and 57.7% for omega-3 FA/placebo among participants at risk of a serious vascular event.

• 7,312 (47.2%) participants were fully adherent to aspirin/placebo during the period at risk of a serious vascular event (SVE)
• 8,937 (57.7%) participants were fully adherent to omega-3 FA/placebo during the period at risk of a SVE
• The trial included 15,480 adults with diabetes using mail-based remote methods
• Adherence was estimated from 6-monthly follow-up forms and the supply of study treatment packs
• A binary adherence variable (full versus less than full adherence) was investigated using logistic regression

Women were significantly less likely to be fully adherent than men for both aspirin and omega-3 FA randomisations.

• For aspirin randomisation: 2,509 (43.3%) women vs. 4,803 (49.6%) men were fully adherent; OR 0.73; 95% CI: 0.68 to 0.80; P < 0.0001
• For omega-3 FA randomisation: 3,035 (52.4%) women vs. 5,902 (61.0%) men were fully adherent; OR 0.67; 95% CI: 0.61 to 0.72; P < 0.0001
• The association between female sex and lower adherence was consistent across both treatment randomisations

Adherence decreased with increasing frailty as measured by the Hospital Frailty Risk Score.

• A statistically significant trend was observed for both treatment randomisations (trend p-value < 0.0001)
• Hospital Frailty Risk Score was one of the potential predictors of adherence considered in the logistic regression model
• The association was present for both aspirin/placebo and omega-3 FA/placebo adherence

Smoking status was associated with lower adherence to allocated treatment.

• Smoking was significantly associated with lower adherence (p-value < 0.0001) for both treatment randomisations
• Smoking status at study entry was one of the predictor variables considered in the logistic regression analysis

Higher predicted 5-year vascular risk score was associated with lower adherence to allocated treatment.

• Vascular risk score was significantly associated with lower adherence (p-value < 0.0001)
• Predicted 5-year vascular risk was one of the potential predictors considered in the logistic regression model

Greater socioeconomic deprivation as measured by the Townsend index was associated with lower adherence.

• Deprivation was significantly associated with lower adherence (trend p-value = 0.0211, p = 0.0011)
• Townsend index was used as the measure of deprivation in the logistic regression model

The large mail-based ASCEND trial achieved adherence comparable to less streamlined trials in similar populations.

• ASCEND used mail-based remote methods to conduct the trial in 15,480 adults with diabetes
• The authors state the trial has 'comparable adherence with less streamlined trials in similar populations'
• The trial assessed two separate randomisations: aspirin versus placebo and omega-3 fatty acid supplementation versus placebo