by José Luis Cárdenas Tomažič

Adapted from the Spanish column originally published in El Economista on May 5th, 2023 (Adherencia a la terapia: el último y fundamental eslabón, que está roto)

Public debate and policymaking across much of the world regarding access to medicines typically focuses on the need to increase health budgets for their purchase and improve spending efficiency, alongside better public procurement, pricing, and waiting lists to obtain them. However, little attention is paid to the final—and most important—part of this long and complex chain: adherence to therapy. Why is that?

Adherence to therapy is a fundamental factor in the effectiveness of medical treatments. It refers to a patient’s ability to follow medical recommendations and prescriptions regarding the use of medicines, therapies, and lifestyle changes. What might seem rather trivial is not; today it has become a global challenge, as adherence rates vary widely depending on the disease, geographic region, socioeconomic segments, among other factors.

There are different types of non-adherence, ranging from cases where a physician issues a prescription that the patient never initiates, to situations where instructions are not followed correctly or the therapy is discontinued—often without the involvement or awareness of the treating physician.

According to the World Health Organization (WHO), lack of adherence to medical treatment is a major global issue. It is estimated that fewer than 50% of patients with chronic diseases such as diabetes, hypertension, and HIV properly follow their treatments. Adherence rates are even lower in low- and middle-income countries, where financial, logistical, and cultural barriers can limit access to medicines and health education. Likewise, adherence tends to be higher among patients with acute conditions than among those with chronic diseases.

Optimal adherence to therapy can vary depending on the disease, treatment, and patient. In general, an adherence rate of 80% or higher is considered necessary to achieve optimal therapeutic outcomes. This means that the patient follows the recommended treatment at least that percentage of the time. However, in the case of HIV or diabetes, even higher adherence is required. For example, adherence of 95% or more has been shown to be necessary for sustained viral suppression in patients with HIV receiving antiretroviral therapy.

Poor adherence can have serious consequences for patient health, increasing the risk of complications and hospitalizations. It can also raise healthcare costs and reduce treatment effectiveness, negatively impacting patients’ quality of life and overall public health.

Several factors influence non-adherence, including simple forgetfulness about the correct dose and timing; side effects that affect quality of life, leading patients to discontinue therapy; treatment complexity, such as multiple medications, several daily doses, or specific dietary rules; lack of support networks such as caregivers; the cost of therapy; and even cultural factors.

As early as 2005, a group of scientists led by Ashish Atreja proposed a set of interventions summarized by the acronym “SIMPLE”:

• Simplify the regimen to fit the patient’s lifestyle;
• Impart knowledge to ensure information meets patient needs;
• Modify beliefs, taking into account culture and individual values;
• Provide communication effectively with patients and families, through active listening and clear messages;
• Leave bias behind, understanding the patient without prejudice;
• Evaluate adherence, working with patients to identify what works for them.

Since these relatively simple recommendations, the field has evolved to include consultancies offering data- and artificial intelligence–based solutions to tailor interventions to the specific causes of non-adherence—although broad, scalable results have yet to be demonstrated.

Regarding how public policy can help, the OECD has emphasized—beyond the personal responsibility of each patient, which is undoubtedly a determining factor—that poor adherence to therapy has rarely been explicitly included in public health policy agendas, which in itself is a problem, perhaps because it is less visible.

It has also noted that policy interventions tend to attribute the issue solely to patients, whereas evidence suggests that health system characteristics—particularly the quality of interaction between patients and providers, prescription renewal processes, and out-of-pocket costs—are key determinants. Finally, patients with chronic diseases often feel excluded from therapeutic decision-making and tend to reject it.

It is evident that low adherence to therapy is affecting both patients and the health system as a whole, yet it remains a topic few wish to address. Without this final link, the costly and complex chain of access to medicines breaks down. Either we all engage more—at a personal level, as healthcare professionals, and at the policy level by implementing effective measures—or we will continue to waste health, lives, and resources before our very eyes.