NEW YORK (Reuters Health) - Just half of people who are given a prescription to prevent heart disease continue to get their medications refilled over time, according to a new review of several studies.
And among people who have already had a heart attack, one out of every three fails to continue getting their prescription refilled.
"Even if these estimates were half as great, the cost of nonadherence is substantial," the group, led by Dr. David Wald at Queen Mary, University of London, writes.
The researchers estimate in their report in the American Journal of Medicine that 130,000 people die each year because they don't adhere to their prescriptions.
The researchers collected the results from 20 studies that suggested the rate at which people continue taking the drugs ranges from 30 to 80 percent.
The studies looked at seven medications, including aspirin, blood pressure drugs, and cholesterol-lowering statins, typically intended for life-long use.
Of the more than 376,000 people in the studies, about 275,000 were given a prescription to prevent heart disease while the other 101,000 were already diagnosed with heart disease.
All of the patients were followed for at least 12 months. Overall, 57 percent of people continued to refill their prescriptions for the drugs.
"This is something that's been going on for decades and we've been well aware," said David Blackburn, an associate professor of pharmacy and the research chair in patient adherence at the University of Saskatchewan in Canada, who was not involved in the research.
Despite it being commonly understood that patients don't always follow the doctors' orders, Blackburn said there are few interventions known to consistently help patients stay on track with their medications.
That's because it's not entirely clear why patients don't stick to their prescriptions, he said.
In some cases, it could be related to the patient - difficulty reading the drug label or opening the container, fear of side effects, or challenges making it to the pharmacy for a refill.
The health care system could play a role too.
"It's difficult to have real a discourse with a physician because... everybody's busy," Blackburn told Reuters Health. "Because of the system and the constraints on cost and time, I think what you end up with are people who are really inadequately prepared" to follow through with their prescriptions.
For the most part, patients complied with their prescriptions at about the same level for each of the different types of drugs.
The only difference was among people without a diagnosis of heart disease, who were less likely to continue taking a water pill than a blood pressure medication known as an angiotensin receptor blocker.
"This suggests that specific drug properties (such as how often people have to take them or side effects) have a minor influence on whether patients remain on treatment long-term," the authors write.
Blackburn said the findings support his ideas of what causes people to drop off of their medications.
"It's probably system-related factors that are so important that they dwarf these little tolerability issues. They get drowned out by the way prescriptions are given and the time we have to engage with people," he said.
He said he thinks that frequent follow-ups with patients to make sure they're continuing their medication is important to help people stay on track.
"It reflects buy-in from patients and prescribers that indeed this is an important thing," he said.
SOURCE: bit.ly/LFAjBc The American Journal of Medicine, online June 27, 2012.