July 17th, 2013

Stroke Risk Increases with Nonadherence to Antihypertensive Therapy

A large new observational study demonstrates that people who don’t take their antihypertensive medications are much more likely to have a stroke. The new study, published in the European Heart Journal, used nationwide prescription, hospital, and mortality records from 73,527 hypertensive patients in Finland.

The investigators compared 26,704 patients who were hospitalized for or died of stroke with 46,823 patients who did not have an event. The stroke patients were older, were less educated, had lower income, and were more likely to have diabetes or cancer than controls.

After adjustment for baseline differences between the groups, patients who were nonadherent were two to four times more likely to die from stroke or be hospitalized for stroke than their adherent counterparts. Here are the adjusted hazard ratios for the nonadherent group at several time-points after receiving the initial antihypertensive prescription:

Adjusted hazard ratios for stroke death after

  • 2 years: 3.81, CI 2.85 – 5.10
  • 5 years: 3.68, CI 2.92–4.65
  • 10 years: 3.01, CI 2.37–3.83

Adjusted hazard ratio for stroke hospitalization after:

  • 2 years: 2.74 (95% CI: 2.35–3.20)
  • 5 years: 2.28 (95% CI: 2.00–2.60)
  • 10 years: 1.71 (95% CI: 1.49 – 1.96)

During the year of death, the nonadherent group had a 5.7-fold increase in risk compared with the adherent group. At each level of nonadherence, the risk for both fatal and nonfatal stroke increased.

The authors note that it is difficult to obtain high-quality evidence about a subject like adherence: “Given that randomization to different adherence groups is unethical, it is unlikely that trial evidence will be available on the effect of adherence to antihypertensive medication on fatal or non-fatal stroke events.”

The lead author of the study, Dr Kimmo Herttua, said in a press release: “These results emphasize the importance of hypertensive patients taking their antihypertensive medications correctly in order to minimize their risk of serious complications such as fatal and non-fatal strokes. Non-adherent patients have a greater risk even ten years before they suffer a stroke. We have also found that there is a dose-response relationship, and the worse someone is at taking their antihypertensive therapy, the greater their risk.”

Said Herttua: “As far as we know, this study is unique as it is the first study to follow patients over a long period of time, repeatedly checking how correctly they are taking their medications, and linking the trajectory of adherence with the risk of fatal and non-fatal stroke.”

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