In most industrialised countries more men die from coronary heart disease than women but what causes these sex differences? The most widely accepted explanation is that the hormone oestrogen protects women, yet a study in this week's BMJ suggests that sex differences are largely the result of environmental factors. If so, it may be possible to reduce deaths in men to levels similar to those found in women.
Using several national and international data sources, researchers at Bristol University examined trends in deaths from coronary heart disease in men and women from different countries. From 1949, in England and Wales, these trends show a marked increase of deaths among men, peaking in the early 1970s. Rates in women over the same period were stable or declined. Similar trends were seen in Australia, France, Sweden, and the United States.
A protective effect of oestrogen alone cannot explain these trends because it is inconceivable that levels of oestrogen in women have changed dramatically over the past century or vary greatly among women of different countries, say the authors. Instead, they are largely the result of environmental factors that affect only men.
Understanding more about the factors that cause the sex differences in deaths from coronary heart disease has important public health implications, particularly in countries or parts of countries where death rates for coronary heart disease are currently increasing, they conclude.