Poor access to primary care physicians and patients' own unwillingness to stick with treatment both appear to play a role in cases of severe, uncontrolled high blood pressure, a study published Thursday concludes.

The research, conducted at two New York City hospitals, found that the chance of having high blood pressure that needs emergency treatment was about four times higher among people who do not have primary care doctors.Those who failed to comply with treatment, such as taking medicines, had double the risk of this severe degree of the disease. "Characteristics of both the health-care system and patients' behavior are associated with severe, uncontrolled hypertension," the doctors wrote.

The findings were based on a study of 93 patients with severe high blood pressure who were treated at Presbyterian Hospital and Harlem Hospital Center.

They were compared with 114 other patients with high blood pressure. All were black or hispanic.

The study, directed by Dr. Steven Shea, was published in the New England Journal of Medicine.

Nearly all of the patients with severe forms of the disease already knew that they had high blood pressure.