Patients with existing diseases unrelated to high blood pressure may be less likely to receive intensive high blood pressure treatment, according to a new study published in the Annals of Internal Medicine.

Researchers from the University of Pennsylvania School of Medicine examined the case records of more than 15,000 patients from six independent outpatient care clinics in the greater Philadelphia area. They found that about 60% of the patients with high blood pressure also had at least two unrelated illnesses (illnesses not connected to or affecting blood pressure).

Unexpectedly, while analyzing the data investigators found that as the number of other, unrelated illnesses rose, the odds that patients would receive intensive high blood pressure treatment fell. Though no firm conclusions are suggested by the study, the authors speculate that the other illnesses may create a "shadow effect" where doctors are hesitant to be too aggressive with blood pressure treatment because of possible negative effects on the other illnesses.

The study, encouragingly, also found that those with diseases related to high blood pressure (diabetes, circulation problems, heart disease) were significantly more likely to receive intensive treatment for high blood pressure.