Many Kiwis prescribed statins to prevent serious health problems such as heart attacks and strokes don't take them as prescribed, new research has found.
Doctors are now trying to figure out why, saying it's a waste of money and putting at-risk groups like Māori and Pasifika at risk.
More than half-a-million Kiwis are prescribed statins to lower their cholesterol levels. Some have had a heart attack or stroke before ('secondary prevention'), and others haven't, but are deemed at risk ('primary prevention').
Researchers from the University of Otago looked at data showing whether patients were taking their medicines as prescribed. They found 37 percent of those who'd never had a heart attack or stroke before weren't taking them optimally, while 41 percent had discontinued their medication for at least 90 days once or more.
Those who'd had a heart attack or stroke before were better - but still 23 percent weren't taking them optimally, and 26 percent had stopped for 90 days or more.
"A cardiac event or a stroke is not really a hypothetical - they're quite motivated, they know what's at risk," said study co-author Simon Horsburgh, senior lecturer in epidemiology at the university's Department of Preventive and Social Medicine.
"People in primary prevention, they're potentially at quite high-risk of one of these events."
Particularly if they're not taking the medication consistently.
"These are effective medications... and [you're] certainly getting much less benefit from them if you're not taking them consistently."
Māori and Pasifika were more likely to lapse in their adherence to doctor's orders, the research found, Dr Horsburgh calling the differences "deeply concerning".
Nearly 39 percent of Māori and 45 percent of Pacific patients taking statins for primary prevention stopped taking it, compared to only 26 percent of Pakeha.
"Statins are a very important medicine.. .but medicines in general are one of the key interventions we use to try and improve people's health in New Zealand, so it's really important that we understand what are the drivers of adherence are so that we're getting the optimal benefit out of these medicines," said Dr Horsburgh.
"If we don't understand those, we're going to be spending a lot of money on these medicines and not achieving very equitable outcomes across population groups in New Zealand."
He said there's already a lot of evidence showing minority groups such as Māori and Pasifika have trouble accessing healthcare.
"This is of particular concern when these groups are also at greater risk of death from cardiovascular disease. These findings feed into the already-large literature highlighting the inequities of healthcare service experience, particularly for Māori and Pacific people."
The study was published this week in journal PLOS One.