Missing blood pressure tablets may have a much bigger effect on heart health than many patients realize.
A major analysis of randomized clinical trials found that people who regularly took their assigned blood pressure treatment had larger reductions in blood pressure and fewer serious cardiovascular events than people who took their medication less consistently.
The findings are being presented at ESC Congress 2026. The research was led by Qianqian Yang of the University of Oxford and examined data from more than 91,000 people who had participated in nine clinical trials.
High blood pressure, also called hypertension, is one of the world’s most common health problems. An estimated 1.4 billion adults between the ages of 30 and 79 have the condition, yet many people do not know they have it because hypertension often causes no obvious symptoms.
Over time, excessive pressure inside blood vessels can damage the heart, brain, kidneys and arteries. It is a major risk factor for heart attack, stroke, heart failure and other serious diseases.
Blood pressure-lowering medicines can greatly reduce these risks when they are taken properly. However, researchers estimate that around half of patients do not take their medication exactly as prescribed.
There are many reasons for this. Some people simply forget doses, while others stop taking medicine because they feel well, worry about side effects, find the treatment complicated or have difficulty paying for or accessing their prescriptions.
Previous studies have linked poor medication adherence with worse health outcomes. However, many of those studies were observational, making it difficult to know how much of the difference was actually caused by missing medication.
People who regularly take their medicine may also differ from people who do not in other ways. For example, they may follow healthier lifestyles, attend medical appointments more regularly or have different health conditions.
To obtain stronger evidence, Yang and colleagues analyzed individual participant data from nine randomized clinical trials. Together, the trials included 91,339 people.
In the original trials, participants received either a blood pressure-lowering treatment or a comparison treatment. The comparison could be a placebo or a less intensive blood pressure treatment.
The researchers then examined how consistently people took their assigned treatment. Participants who took at least 80% of their assigned medication were placed in the higher-adherence group, while those who took less than 80% were considered to have lower adherence.
Even within clinical trials, where patients are usually monitored more closely than they would be in everyday medical care, adherence declined over time. About 88% of participants met the higher-adherence definition during the first year, but that figure fell to 79% by the fifth year.
The difference in blood pressure response was clear. Among people with higher adherence, the more intensive treatment reduced systolic blood pressure by 5.2 millimeters of mercury more than the comparison treatment.
Systolic pressure is the upper number in a blood pressure reading. It measures the pressure in the arteries when the heart contracts and pushes blood around the body.
Among people with lower adherence, the difference between the treatment and comparison groups was only 3.0 millimeters of mercury. This suggested that inconsistent use reduced the ability of the treatment to control blood pressure.
The researchers then examined serious cardiovascular outcomes. These included stroke, heart attack or ischemic heart disease, as well as heart failure that resulted in hospitalization or death.
Among people with higher medication adherence, the intervention treatment was associated with an 11% lower incidence of major cardiovascular disease compared with the control treatment. Among those with lower adherence, there was no statistically significant reduction.
Yang said the findings reinforce a simple but important principle: medicines cannot provide their full benefit when patients do not take them. People with good adherence gained larger blood pressure reductions and greater protection from cardiovascular events.
The results also show that adherence is not merely a problem outside research settings. Even people enrolled in structured clinical trials became less consistent about taking medication as the years passed.
This matters because hypertension treatment is often lifelong. A patient may take tablets reliably for the first few months after diagnosis but gradually begin skipping doses once the condition feels less urgent, particularly because high blood pressure itself may not cause noticeable symptoms.
The researchers argue that checking medication adherence should become a more routine part of hypertension care. Instead of assuming that a medicine has failed, clinicians may need to ask whether patients are able to take it consistently and what is making that difficult.
There are practical ways to make treatment easier. Doctors can sometimes simplify complicated medication schedules, prescribe combination tablets that contain more than one medicine, or choose longer-acting drugs whose effects may be less disrupted by an occasional missed dose.
Professor Felix Mahfoud, chair of the European Society of Cardiology Communication Committee, said health professionals have often overlooked nonadherence as a reason for uncontrolled hypertension. He emphasized the importance of open and nonjudgmental conversations about the barriers patients face.
The study has an important strength because it used patient-level information from randomized trials rather than relying entirely on ordinary observational data. Its very large sample also allowed researchers to examine differences in cardiovascular outcomes as well as changes in blood pressure.
However, the analysis does not mean that every missed tablet immediately causes a heart attack or stroke. Medication adherence is complex, and the effect of an occasional forgotten dose may differ depending on the medicine, dose, person’s health and how often doses are missed.
The 80% cutoff also divides adherence into two broad categories, while real-world behavior is more complicated. Someone taking 79% of doses may not be biologically very different from someone taking 81%, and future research could provide a more detailed picture of how different patterns of missed doses affect risk.
Overall, the findings offer strong evidence that taking blood pressure medication consistently is a central part of receiving its cardiovascular benefits. They also suggest that improving adherence may be one of the simplest opportunities to prevent strokes, heart attacks and heart failure in people who already have effective medicines available to them.
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Source: University of Oxford.
