Epidemiology of hypothermia: fatalities and hospitalisations in New Zealand.

BACKGROUND: Hypothermia occurs within domestic and non-residential settings. Most epidemiological data originate from the northern hemisphere, with little data being generally available concerning cases from New Zealand and Australia. AIMS: The National Health Statistics Centre (New Zealand) records hospital discharges and deaths. This study isolated hypothermia cases, to quantify its incidence and identify risk groups.
METHODS: The morbidity and mortality files for the years 1979-86 (cases = 3,808,717) and 1977-86 (cases = 259,325; respectively) were searched by three investigators.
RESULTS: Hypothermia hospitalisations were identified (6.9 per 100,000 per year). There were 176 deaths from hypothermia, representing 0.07% of the 259,325 deaths from all causes for the same period (0.537 per 100,000 people per year); of these fatalities, 72.2% were classified as domestic, and 27.8% as non-residential; of the domestic fatalities, 86.6% were 65 + years and 35.5% of these were male. Within the non-residential category, 75.5% were aged 13-65, of which 94.6% were male. The hospitalisation incidence was 12.7 times the fatality incidence, with the majority of hospitalisations being of domestic origin (88.4% of total), and occurring mostly within the lower and upper age extremes. Neonatal domestic hypothermia accounted for 72.6% of all domestic hospitalisations, and the elderly constituted 72.0% of the remaining cases. The proportion of New Zealand fatalities caused by hypothermia was 0.067%; lower than reported in the United Kingdom.
CONCLUSIONS: The two main non-neonatal groups contributing to cases of hypothermia were males aged 13-65 years, and the elderly. In the aged, the proportion of hypothermia-related deaths was no different from that associated with other disorders, however, the case-fatality ratio was three times greater, highlighting the need for improving prevention and management strategies.