Patients with chronic health problems who play a major role in their medical treatment may have poorer outcomes than patients who defer to their doctors, suggests a U.S. study that tracked 189 hypertension patients for 12 months.

The University of Iowa study found that patients who were more highly involved in their care had higher blood pressure and cholesterol than passive patients, CBC News reported. The involved patients had an average blood pressure of 141 over 70 and low-density lipoprotein ("bad" cholesterol) levels of 122, compared with an average blood pressure of 137 over 72 and an LDL level of 92 for passive patients.

This may be because the more involved patients may have been less satisfied with the medicines prescribed by their doctors and therefore less likely to adhere to the drug regimen, said the authors of the study, published this week in the journal Annals of Behavioral Medicine.

The researchers said the findings suggest that understanding patient preferences for treatment can help doctors tailor therapies to patients and increase the chance of success, CBC News reported.