Patterns of Medication Adherence to Lipid-Lowering Therapy in Primary Care: A Group-Based Trajectory Analysis

Background and objective Despite the widespread use of lipid-lowering medications (LMMs) in primary care, understanding how individuals adhere to these medications and the factors associated with adherence remains limited. This study aimed to identify distinct adherence trajectories and their predictors among adults prescribed LMMs in Australian primary care settings. 

Methods A retrospective cohort study was conducted using data from January 2013 and March 2023. Having at least one medication prescription every six months was defined as medication adherence, considering five repeats/refills associated with prescribing LMMs. Medication adherence trajectories and their predictors were identified using multivariable multinomial logistic regression and group-based trajectory analysis. 

Results Four trajectories were identified among 51,504 individuals (statin users >90%) and included non-adherence (41%), rapid decline (29%), gradual decline (10%), and high adherence (20%). Compared to the high-adherence group, individuals in the non-adherence group were more likely to live in metropolitan areas (adjusted relative risk [aRR] 1.99, 95% confidence interval [CI] 1.73, 2.30), be younger (aRR 0.97, CI 0.96, 0.97) and non-smokers (aRR 0.80, 95% CI 0.70, 0.92), with no history of diabetes (aRR 0.66, 95% CI 0.54, 0.82). Similar results were found when rapid and gradual decline adherence groups were compared to the high-adherence group with the addition of abnormal cholesterol ratio being associated with a higher risk of non-adherence (aRR 1.17, 95% CI 1.01, 1.35). 

Conclusion Our findings highlight distinct risk profiles associated with different medication adherence trajectories in individuals on LMMs. This knowledge will be used to develop targeted interventions to optimise medication adherence.