A new study has found New Zealand has the highest rate of motor neurone disease (MND) of any country in the world.
University of Auckland scientists found the mortality rate for MND in New Zealand is as high as 2.8 deaths per 100,000 people. Internationally, the average is just 1.67 deaths per 100,000 people.
MND is the world's third most-common neurodegenerative disorder, after Alzheimer's and Parkinson's disease.
The symptoms include the gradual degeneration of people's motor neurones: leaving sufferers unable to speak, move, and eventually breath.
The head of the Motor Neuron Disease Research Lab, Dr Emma Scotter, said the study findings can not be just explained by New Zealanders living longer - which they took into their calculations.
"We know that New Zealand doesn't have higher MND mortality rates just due to living longer, or having a greater proportion of older people in our population," Dr Scotter said.
"It's something other than just an age effect."
Our higher mortality rate for MND means that of the 131 people in New Zealand who are lost to MND every year, 53 of these deaths are unanticipated.
The cumulative risk of developing MND over one's lifetime in New Zealand may therefore be even greater than one in 300, the estimated risk internationally.
Scotter's team also found that in Māori, the rate of MND is about half that of the rest of the population.
Researchers say this suggests Māori may have protective factors for MND – or there are healthcare disparities that reduce the number of Māori with MND who are diagnosed properly.
The Centre for Brain Research at the University of Auckland analysed data from 2264 people, for the study, who died from MND between 1992 and 2013.