Pubdate: Nov 28, 1998
Source: New Scientist (UK)
Page: 18-19
Copyright: New Scientist, RBI Limited 1998
Contact:  http://www.newscientist.com/ 
Author: Phyllida Brown

THE CHINESE WAY OF DEATH

FOCUS: We Know That One In Two Smokers Will Die---But How Tobacco
Kills You May Depend On Who You Are And Where You Live

ONE HUNDRED MILLION---or one in three---of today's young Chinese men
are expected to die from cigarette smoking in the next few decades.
But these grim numbers, announced last week after unprecedented
large-scale studies of China's smoking epidemic, are not completely
unexpected. What has surprised researchers are the different ways in
which tobacco produces its fatal effects there, compared with the West.

In the US and Britain, whose smoking epidemics have reached their
peak, about half of all regular long-term smokers eventually die of
their habit. Among Chinese long-term smokers, the same proportion is
eventually expected to die when the epidemic there reaches the same
stage in a few decades. But for the time being, at least, the diseases
that kill smokers in China follow a strikingly different pattern, with
respiratory diseases the most important cause of death and
tuberculosis killing as many smokers as heart disease (see Diagram).

The bottom line, then, is that smoking is at least as dangerous
overall as anyone thought. But rather than causing specific diseases,
instead it seems to increase the fatalities due to the chronic
diseases that predominate in any given population, says Richard Peto,
one of the authors of the study and an epidemiologist from the
University of Oxford.

A leaked memo reveals that British American Tobacco has already tried
to exploit differences in the patterns of tobacco-related diseases in
China and the West. But while tobacco firms are likely to cite the
latest findings as evidence that tobacco does not cause specific
diseases, Peto is unfazed. He argues that the size of the numbers and
the strength of the link between smoking and death are overwhelming.
"Tobacco is something that makes a particular disease a lot more
common, which means that it is an important cause of deaths from that
disease," he says. He notes the risk of dying from respiratory disease
or cancer increases with the length of time someone smokes, further
implicating tobacco in each death. And he argues that almost no
disease has a single cause and that it is bad science to suggest it
does.

The long-term implications of the findings from China are clear.
First, they show that no developing country can afford to extrapolate
from Western figures to predict the shape of its tobacco epidemic.
Second, they suggest that public health officials may need to rethink
their approaches to treating and preventing diseases such as
tuberculosis, which kills 2 million people a year.

There were two main studies in China--- both conducted by teams in
Beijing at the Chinese Academy of Preventive Medicine and the Chinese
Academy of Medical Sciences, along with Peto and others in Britain and
the US. Both appear in last Friday's British Medical Journal (vol 317,
p 1411 and 1423). In the first, an industrial-scale endeavour,
researchers traced the death certificates of almost one million people
who had died between 1986 and 1988 across the country, in 98 rural and
urban districts that are broadly representative of the country as a
whole. This was possible because, unlike most poor nations, China
counts its dead.

A surviving relative of each dead person was contacted by medical
staff and asked whether the dead person had smoked or not. The
researchers sorted the death certificates into four groups: cancers,
respiratory disease, vascular disease (heart disease, strokes and
other circulatory disease) and "all other" causes.

They used the other-causes group as a reference group that enabled
them to see how over-represented smokers were in each of the cancer,
vascular and respiratory disease groups and therefore calculate the
fraction of deaths in these groups due to smoking.

The second "smaller" study is still under way. It involves 250 000
adults whose smoking habits have been recorded and whose deaths are
being monitored. Results from the first 10 000 deaths align closely
with those of the first study. Both investigations show that today
about 12 per cent of Chinese male deaths are caused by tobacco. For
women, the figure is 3 per cent, but, unlike most regions studied, and
to everyone's surprise, young Chinese women seem to be giving up smoking.

In terms of the overall numbers, the results are an uncanny echo of
the tobacco epidemic in the West. In the US, tobacco was responsible
for 12 per cent of all deaths in 1950, when cigarette consumption was
at its peak. Twenty years on, after the long incubation of many
smoking-related diseases, tobacco-related deaths in America had risen
to 33 per cent of the total. In China, cigarette consumption among men
is now at the same level as in the US in 1950, and, from the
calculations of both studies, the same proportion of all deaths, 12
per cent, are attributed to smoking. If the pattern persists, then
tobacco-related deaths in Chinese men will rise like those of the US
to reach one in three in the next few decades. The proportion of
smokers killed by their habit will rise, as in the US, from one in
four to one in two.

But that's where the similarity with the West ends. In developed
countries, lung cancer in nonsmokers is rare, and smoking increases
the risk that a person will die of the disease about twentyfold. In
China, lung cancer is comparatively common, even among nonsmokers, and
smoking "only" trebles the risks. For reasons that no one can explain,
the rates of death from lung cancer in nonsmokers also vary tenfold
across the country. Peto thinks part of the explanation may be the
heavy indoor air pollution in some of the colder cities, such as
Harbin, where people heat their homes and cook with coal. This
illustrates the problem of making direct comparisons between East and
West.

The picture for heart disease is even more puzzling. In the West, in
young middle age, a smoker's risk of dying of heart disease is 300 per
cent greater than a nonsmoker's. In China, it is a mere 30 per cent
greater for the smoker. "This finding was completely unexpected," says
Peto. "I was very uncomfortable with it, and thought, 'What have we
done wrong?"' In fact, the prospective study and the retrospective
study tie up so closely that the researchers are now confident that
they have got their epidemiology right. They hope further studies will
shed light on these observations.

Other researchers, such as Paul McKeigue at the London School of
Hygiene and Tropical Medicine, say that the results for heart disease
should not be so surprising because heart disease is relatively
uncommon in China compared with the West. The causes of heart disease
are still not fully understood, and it is possible that smoking in
Western societies simply exacerbates a disease that is already very
common.

These studies raise many questions about the ways smoking kills in
different populations. But they nonetheless show cigarettes are
killing vast numbers in the developing world, and that by 2025 tobacco
will probably kill as many people in a year as the current annual
death toll from diarrhoeal disease, pneumonia, malaria and TB
combined---around 10 million people.

On 22 November at Beijing's Tsinghua University, WHO leader Gro
Harlem Brundtland launched the organisation's latest anti-smoking
initiative. She told the Chinese premier Zhu Rongji there is no
greater priority in global public health than reversing the trend of
rising tobacco consumption in the developing world--- and she now has
the evidence to back her claim.
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Checked-by: Patrick Henry