New research from the Netherlands suggests patients with high blood pressure who actually take their prescribed medications are few and far between, a surprising reality that can be dangerous and deadly for high-risk patients.

The research, published in Hypertension, showed that 20 percent of patients with hard-to-control high blood pressure were taking all their medications, while another 20 percent took none for resistant hypertension, which is classified as dangerously high blood pressure.

The study was initially designed to determine if resistant blood pressure could be lowered with medication and renal denervation, a blood vessel catheter procedure that destroys sections of nerve messages corresponding between the brain and kidneys.

“There is much evidence to suggest that these nerves play a role in high blood pressure,” said Peter Blankestijn, MD, PhD, an author on the study and a professor of nephrology and hypertension at the University Medical Center Utrecht in the Netherlands, in a statement. “In the 1930s and 1940s, the nerves were sometimes cut during surgical procedures. Now the nerve destruction can be done in a much less invasive way. Several devices are being studied as possible treatments for resistant hypertension.”

In the study, Blankestijn and his team randomly assigned 95 patients to undergo renal denervation while remaining consistent with their medication regimens. A control group of 44 patients continued taking their usual medications with no additional changes.

Throughout the study, patients wore a blood pressure monitor and blood tests were regularly taken to measure medication levels in their blood. Results showed that 31 percent of patients improved or lessened their medication compliance. However, after six months, average blood pressure decreased more in control patients than in those who had renal denervation. But overall, blood pressure remained abnormally high in both groups.

“Adherence to medication greatly affects the ability to assess the value of another treatment, so researchers need to measure adherence and do what they can to improve it,” Blankestijn said.

He said that if patients are adamant about not taking medications, they need to at least notify providers so that they can together find a more suitable and healthy treatment plan.

“You and your doctor can discuss options for changing the type of pill or the dose if needed,” Blankestijn said. “There are many effective blood pressure pills, and the majority of patients with high blood pressure can be successfully treated.”