Trends in head injury incidence in New Zealand: a hospital-based study from 1997/1998 to 2003/2004

Traumatic brain injury (TBI) is a leading cause of disability and death in young adults. Globally, the incidence of TBI hospitalizations is estimated at 200-300 people per 100,000 annually. Using a national health database, we examined the incidence of TBI-related hospital discharges (including 1-day stays) to New Zealand Hospitals from 1997/1998 to 2003/2004. Crude annual hospital-based incidence rates for the total population ranged from 226.9 per 100,000 in 1998/1999 to a high rate of 349.2 in 2002/2003. There was a noticeable increase in rates with the change from ICD-9 to ICD-10 diagnostic codes and there was also disparity in incidence rates according to ethnicity, age and gender. Crude annual hospital-based incidence rates for males and females in Maori (689/100,000 and 302.8/100,000 person-years) and Pacific Island populations (582.6/100,000 and 217.6/100,000 person-years) were much higher than those for the remaining population (435.4/100,000 and 200.9/100,000 person-years), particularly for males. The overall age-standardized hospital- based incidence rate for 2003/2004 was 342 per 100,000 per year (95% CI = 337-349/100,000), and 458 per 100,000 per year for Maori (95% CI = 438-479/100,000) with Maori males experiencing a peak in incidence between 30 and 34 years of age that was not evidenced for the wider population. Standardized hospital-based incidence rates for the total population and for Maori by age, gender and ICD-10 diagnostic codes are also examined.