Non-adherence to medication increases stroke risk in patients with high blood pressure

BMJ 2013; 347 doi: (Published 17 July 2013) Cite this as: BMJ 2013;347:f4586
  1. Susan Mayor
  1. 1London

Patients with high blood pressure who do not take their antihypertensive medication as recommended have a nearly fourfold increased risk of dying from a stroke by the second year after being prescribed treatment compared to those who do, a study has found.1

Researchers used nationwide registers in Finland that give details of anonymised individuals on medication, admissions to hospital, and deaths from 1 January 1995 to 31 December.

They assessed adherence to antihypertensive medication by tracking the number of prescriptions filled for the 73 527 people aged 30 years or older diagnosed with and prescribed drug treatment for high blood pressure. Adherence was classed as good if patients took their tablets correctly more than 80% of the time. Non-adherence could be intermediate (taking tablets correctly 30% to 80% of the time) or poor (less than 30%).

The results showed that patients who did not adhere to their medication had a nearly fourfold increased risk of dying from stroke in the second year after first being prescribed antihypertensive drugs compared with adherent patients (odds ratio 3.81 (95% confidence interval 2.35 to 3.20)). Non-adherent patients also had a threefold increased risk of dying in the tenth year (odds ratio 3.01 (2.37 to 3.83)).

The study, which was funded by Finnish and UK academic and national funding bodies, also found that patients who did not adhere to their medication were more likely to be admitted to hospital after a stroke. And non-adherence was associated with a 5.7-fold increased risk of fatal stroke during the year of death (odds ratio 5.68) and a twofold increased risk of non-fatal stroke. Risks were even higher in patients with poor adherence.

In the year of an event, the odds risk of stroke death in patients with poor adherence was 7.99 (6.28 to 10.18) times higher than in those with good adherence. The corresponding odds ratio for patients with intermediate adherence was 3.60 (2.95 to 4.39).

The study’s lead author, Kimmo Herttua, a senior fellow in the population research unit at the University of Helsinki in Finland, said, “These results emphasise the importance of hypertensive patients taking their antihypertensive medications correctly in order to minimise their risk of serious complications such as fatal and non-fatal strokes.

“We have found that there is a dose-response relationship, and the worse someone is at taking their antihypertensive therapy, the greater their risk.”

He noted that this was the first study to track the impact of adherence with antihypertensive drugs and stroke in individuals over time.


Cite this as: BMJ 2013;347:f4586