Poor adherence to blood pressure medication may significantly reduce its ability to prevent heart attacks, strokes and other cardiovascular complications, a major analysis of clinical trial data has found.
The study, involving 91,339 patients across nine randomised trials, found that people who consistently took their antihypertensive drugs had greater reductions in blood pressure and cardiovascular events than those who missed doses.
The findings are particularly important as an estimated 1.4 billion adults aged 30 to 79 worldwide live with hypertension, while about half of patients do not take their medication as prescribed.
Presenting the findings, Qianqian Yang of the University of Oxford, UK, said the analysis provided stronger evidence of the consequences of poor adherence than previous observational studies.
Researchers classified patients who took at least 80 per cent of their prescribed treatment as having high adherence, while those taking less than 80 per cent were considered to have low adherence.
Among patients with high adherence, systolic blood pressure fell by 5.2 mmHg in those receiving the antihypertensive intervention, compared with the comparator group.
For patients with low adherence, the reduction was just 3.0 mmHg.
Adherence also declined with time, even under the controlled conditions of clinical trials. The proportion of patients with high adherence dropped from 88 per cent in the first year to 79 per cent by the fifth year.
The researchers also examined major cardiovascular disease, including stroke, myocardial infarction, ischaemic heart disease and heart failure resulting in death or hospitalisation.
They found an 11 per cent reduction in major cardiovascular disease among patients with high adherence who received the intervention.
However, no significant cardiovascular benefit was seen among those with low adherence.
Yang said the findings reinforced a basic principle of treatment: medicines cannot provide their full benefits when patients do not take them as prescribed.
The researchers urged healthcare providers to make medication adherence a routine part of hypertension care and to identify barriers that prevent patients from taking their drugs regularly.
They recommended simplifying treatment regimens, using single-pill combinations to reduce medication burden and considering longer-acting medicines where appropriate.
Professor Felix Mahfoud, Chair of the European Society of Cardiology Communication Committee, said non-adherence had long been overlooked as a cause of uncontrolled hypertension.
He urged healthcare professionals to have open, non-judgemental conversations with patients about difficulties they may face in taking their medication, stressing that better adherence could help patients benefit fully from life-saving treatment.
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