The number of New Zealanders with traumatic brain injuries has reached "epidemic levels", with a new injury occurring on average every 15 minutes, a world-first study has revealed.
The number is significantly higher than in other developed countries, and children, young adults, men, Maori and rural inhabitants are most at risk of sustaining one, Auckland researchers found.
Previous statistics "grossly underestimated the extent of traumatic brain injury in New Zealand", said lead researcher Professor Valery Feigin from AUT University's National Institute for Stroke and Applied Neuroscience.
Instead the research, published today in prestigious international medical journal The Lancet, found that each year an estimated 36,000 new traumatic brain injuries (TBI) occur - far surpassing the number of heart attacks and more than five times the number of new strokes.
Most were due to falls, 38 per cent, followed by mechanical forces, transport accidents, and assaults.
Strategies are urgently needed to reverse this "silent epidemic", said Professor Feigin.
A TBI is caused by an external force, such as a bump or blow to the head, which disrupts the normal function of the brain.
The effects range from mild memory difficulties to dementia, seizures and depression.
"Often people with head injuries don't realise they've had a brain injury. Anyone with a head injury resulting in losing consciousness or being dazed and confused should seek medical attention immediately,"said Professor Feigin.
The study looked at the incidence of TBI in more than 173,200 Waikato residents between 2010 and 2011.
Rates of injuries in New Zealand, 790 cases per 100,000 people each year, were far higher than other developed countries in Europe, 47-453 cases per 100,000 people and North America (51-618 cases).
Brain injuries, including stroke and traumatic brain injury, is the leading cause of disability and death in New Zealand.
Previous figures put the estimated cost on the health system as $100 million a year, said Professor Feigin, but he expected this figure to rise significantly.
Researchers also found the number of mild traumatic brain injuries sustained "alarming", said Professor Feigin.
"The consequences of mild TBI are not mild at all. Generally speaking, mild TBI is characterised by a relatively short loss of memory of the event of the injury or what has happened just after the injury, and/or a very minor loss of consciousness at the time of the injury."