NZ winter death rate high by international standards

Winter is not a good time to get ill in New Zealand, particularly if you are very young or old according to a recent study by the University of Otago. Public health researchers have found that 1600 more people die over the winter months than summer, which puts this country at the upper end of the international scale for excess winter mortality (EWM).

The study analysed monthly mortality rates per 100,000 people between 1980 and 2000. It found that winter rates are 18% higher than in summer and that 9% more females die in winter than males. One alarming finding was that EWM has not declined at all over the last 20 years. This is during a period when most other health indicators have improved.

Associate Professor Michael Baker from the University of Otago, Wellington says that this EWM is 2% higher than the mean mortality rates for 14 European countries, many of which have colder winter temperatures than New Zealand.

"One theory is that countries like Canada, Norway and Russia have such cold winters that people have developed better insulated houses and other strategies to survive winter. More temperate countries like New Zealand, Ireland and Portugal have a higher EWM because we are less well adapted to cold conditions."

Dr Baker says the key now is to try to determine what causes the high winter death rate in this country and to try to reduce the figure by social and health interventions.

"The Housing and Health Research Programme has carried out large community trials showing that insulating houses results in reduced illness rates. The programme has also shown that improved heating reduces asthma attacks. This research needs to be extended to other aspects of housing improvements to see if such interventions can start to reduce this large burden of EWM."

Dr Baker says that the study showed that people are more likely to die in winter from respiratory diseases (66% higher) such as pneumonia and bronchitis, and circulatory diseases (24% higher) such as heart attacks or stroke. He says if people have circulatory problems and serious respiratory diseases, cold winter conditions are likely to make these conditions worse. It is particularly important that we take good care of our elderly family members and friends and make sure they are not spending their winter months living in cold, damp housing.

To find ways of reducing the current high mortality rates will necessitate more detailed research to determine those pathways which lead to winter illness and higher death rates. This research needs to further investigate the role of possible determinants, including climate, influenza, behaviour, crowding, home heating and the thermal performance of houses.

The 'Trends and determinants of excess winter mortality' study is the first of its kind in the southern hemisphere and dovetails with other ground- breaking studies into health and housing being carried out by the Department of Public Health under Professor Philippa Howden-Chapman and colleagues.

This study was published in BMC Public Health and funded by a University of Otago research grant.