Deaths related to epilepsy may be more common than most people realise, researchers say.
Auckland City Hospital doctors have looked at 10 years of data and identified 166 deaths - and they think that's an underestimate.
Study co-author Peter Bergin says it's timely, given the attention on five deaths following Pharmac's funding change to a new drug.
"I don't think we can be sure that that's the explanation," he told Newshub. "People have died from this ever since epilepsy has existed, but it hasn't had a lot of publicity."
Pharmac switched funding from Lamictal and Arrow to Logem - a generic form of the same drug - saying it would save $30 million over five years, that could be spent on other medicines. But after three deaths were linked to the switch, Pharmac in November let people switch back to their original brand. Two more have died since.
But Dr Bergin suspects some prior epilepsy deaths may not have been identified, and the new research shows we can't definitively link the five deaths to the new drug.
In 2013 there were 26 deaths linked to epilepsy alone, and that was well before the drug brands were switched, for example.
Dr Bergin says it's far more common than people think, with perhaps up to 40 deaths in New Zealand a year.
"This study suggests that people with epilepsy who die from SUDEP [sudden unexpected death in epilepsy] in New Zealand are young and are often compliant with their medication... They had seizures because the drug they were on is ineffective. That's one of the questions that we still need to try and address."
Around 0.7 percent of people have some form of epilepsy. Of that population, studies show the rate of SUDEP per year is about 1.2 per 1000 people.
"If the incidence of SUDEP in New Zealand is 1.2 per 1000 people with epilepsy per year, we would expect that approximately 40 people with epilepsy will die annually from SUDEP," the researchers concluded.
"However, in this study, the number of deaths per year ranged from 11 to 26. It is possible that the incidence of SUDEP is declining, but we suspect that not all cases were identified."
The research was published Friday in the New Zealand Medical Journal.