Will men begin to close the age gap as women smoke and drink more? Risteard Mulcahy examines the data
It is common knowledge that women in Ireland and other Western countries tend to live longer than men. Why does this disparity exist?
In 1968, with my colleagues JW McGilvray of Queen's University in Belfast and Prof Noel Hickey of St Vincent's University Hospital and UCD, I looked at the life tables for 15 Western countries from 1920 to 1963. We noted that there was a substantial increase in life expectancy in all 15 countries and in all age groups over this period, mostly accounted for by a fall in infant mortality and the better control of epidemic contagious diseases.
We found during the same time that the excess life expectancy of women over men had increased from a mean of 1.81 years in the early 1920s to 3.72 years in the 1960s.
We had information about the per capita consumption of cigarettes in each of the 15 countries and, for the purpose of correlating the tobacco data with the gender disparity in life expectancy, we assumed that in all countries male smoking was substantially more widespread than female smoking. Using this assumption, we found a significant correlation between total cigarette consumption and the excess female life expectancy at the age of 40.
We concluded the article (published in the American Journal of Public Health in 1969) by saying: "Our results are consistent with the hypothesis that cigarette smoking, because of its association with coronary heart disease and other chronic disorders, may partly or completely account for the better female compared to male life expectancy experienced over the last 50 years."
What has happened since 1963? The excess female to male life expectancy for the 40-year age group in Ireland reached 5.5 years in 1979 and has remained steady until the most recent estimate, in 1996, when it was 5.7 years.
If our assumption of 1969 is correct, and bearing in mind the increase in female and the decrease in male smoking since 1963, we should not be surprised by the unchanged disparity during the past 17 years.
The 1996 estimate confirmed a life expectancy for men from birth of 73 years and for women of 78.7 years (and, at 40 years, of 35 for men and 39.8 for women). The disparity in the life expectancy at birth of the two genders increased from one year to nearly six over 70 years. This must be largely related to men's lifestyles compared to women's. One obvious factor is that men have been substantially heavier smokers.
The next estimate of life expectancy will be available by next year, based on the 2002 census. Life expectancy improved progressively during the 20th century and is likely to have improved further by 2004.
Women are smoking and drinking more in recent years, however, and are adopting other aspects of male lifestyle. (About 30 per cent of men and women are smokers in the Republic.) It is likely, therefore, that the life expectancy disparity between the two sexes will not increase further and may, indeed, contract, particularly because women - with their lighter and smaller mass - are more vulnerable than men to the damaging effects of smoking and excess alcohol. The latest figures from the National Cancer Registry show lung cancer in women is increasing by 3 per cent a year.
Let us suppose that the life expectancy at birth noted in 2004 will have reached 75 for men and 80 for women. If we break down the life expectancy of the population into smokers and non-smokers, we may make an assumption about the non-smokers' expectancy at birth. It is clearly established that a person smoking 20 cigarettes a day from the age of 20 or earlier is likely to reduce his or her life expectancy by 10-15 years. If smokers are excluded from life expectancy estimates, it is likely that, other things being equal, the life expectancy of non-smoking adults could be as high as 77 for men and 82 for women.
Our biological lifespan may well be from 85 to 100 years. Perhaps, if we can identify all the factors that determine health risk in our environment and unravel the mysteries of genetics, we can remain disease-free until we undergo final biological disintegration.
Risteard Mulcahy is professor of preventive cardiology (emeritus)at UCD and St Vincent's University Hospital, Dublin