Adherence

Prevalence of Adherence

The prevalence of medication non-adherence can vary depending on the type of medication(s) under review, the condition(s) for which the medication(s) is/are being used to treat and the population under study.  When regards to the type of medication, important factors to consider are the mode of delivery (tablets, capsules, inhalers) and the complexity of the dosing regimen (once daily vs multiple times per day). Medications with less complex regimens (one pill once daily, no interaction with food/other medications) tend to result in higher adherence than medications with more frequent dosing.[4]

Medication adherence in chronic conditions may be affected by factors such as disease pathogenesis, illness representations (health beliefs) and the presence of co-existing illness or multimorbidity. It is estimated that over 50% of people with chronic disorders are poorly adherent to their medication [5] and this may vary when looking at specific conditions. A pooled analysis of studies that analysed adherence to cardiovascular conditions found that 60% of patients were considered adherent (≥80%) to therapy.[6] Whereas for oral hypoglycaemic medications used in type 2 diabetes mellitus, the prevalence of adherence has been estimated at 68%.[7]

Medication non-adherence may be more of an issue in certain populations such as older people, due to the increased likelihood of polypharmacy and multimorbidity, as well as other socio-demographic variables. Experiencing a major clinical event such as a heart attack may make patients more adherent to secondary prevention medications in comparison to patients who are identified as at risk of a heart attack but have never experienced such an event (primary prevention). Patients who are newly started on a treatment regimen (new users) may have different adherence patterns to those who have been taking the medication(s) for a number of months/years (prevalent users).