Hamish Cooper, of Waihopa School, asks :-

Why do women live longer than men?

Charlotte Paul, an epidemiologist at the Otago Medical School, responded.

In all industrial countries males have higher death rates and shorter life expectancy than females. The difference in life expectancy in New Zealand is now six years. It hasn't always been like this, and in most non-industialized countries today the sex difference is much smaller. In some countries, like India, males live longer than females.

The fact that there are differences between countries and over time shows that the greater male disadvantage seen in New Zealand is not just due to biological or genetic factors but is also due to the environment in which people live.

Genetic factors certainly play some part. Males are vulnerable to X-linked genetic disorders and seem to have less resistance to infections than females. Women's lower rate of heart disease is probably also partly linked to the protective effect of female hormones.

The environment is the most important reason for longer life for women. Women are less likely to have occupations which are dangerous and cause deaths by accidents or cancer. Women have until recently been much less likely to smoke cigarettes than men, and smoking causing lung cancer and heart disease is a major reason for the difference in life expectancy. Women are less likely to drink alcohol heavily or engage in risky and violent behaviour. How much male risk taking and aggression is due to the environment or whether it is in anyway genetic is a matter of ongoing controversy. Health care may also make a difference. It seems that women are more likely to seek help earlier than men.