Monday, March 30, 2015
Tobacco threat still smokes like a dormant volcano
In 2006, I found
myself caught within a crowd of 267,153 fellow New South Welshmen. No, it was
not at a one-day cricket match or even a State of Origin rugby league clash.
All of us were aged 45
years or above — considerably above in my case. We comprised the subjects for a
long-term survey from the Sax Institute, a public health research agency in
Sydney, known as the 45 and Up Study.
It is technically
described as a “cohort study randomly sampled from the general population of
NSW”.
We all completed a health
questionnaire and gave our consent to be followed by repeat surveys and linkage
of our health databases.
We were asked if we
had ever been a regular smoker, at what age we started (if we had), when we
quit (if we had) and how much we had smoked. At baseline, 7.7% of respondents
(aged 38.5 years on average) said they were current smokers and 34.1% were past
smokers.
With a mean follow-up
time of 4.3 years, there had been 5593 deaths. This was a frightening
intimation of mortality for those of us in the study.
When adjusted for
other risk factors, current smokers vs never-smokers had about three times the
risk of dying — a risk that increased with the heaviness of the smoking habit.
“Smokers were estimated to have the same risks of death [about 10] years
earlier than 75-year-old nonsmokers,” the study found.
The good news was that
“for those smokers who quit before age 45, the death rates were similar to
those seen in never-smokers. Mortality diminished progressively with increasing
time since cessation of smoking”.
Related News:
The research team was
led by Professor Emily Banks from the National Centre for Epidemiology and
Population Health in Canberra and the Sax Institute. Renowned Australian epidemiologist
Dame Valerie Beral from the Cancer Epidemiology at the University of Oxford was
also part of the research group. The results were recently published in the
journal BioMed Central.1
"A mature epidemic of tobacco use is not a picnic ground any more than the
side of a seemingly quiescent volcano. People who live near tobacco still
die."
Dame Valerie has a
serious track record for studying the health of women, especially using cohort
studies similar to this one. The idea of such a study is to begin tracking
people while they are well. Then when an illness befalls them, it’s easy to
compare their prior history with that of a person who has remained well,
looking for subtle differences in lifestyle, medications, occupation and so
forth.
The great virtue of
cohort studies is the absence of bias in the selection of the study subjects.
This makes the comparison of individuals years down the track easier: the
researcher and the subject are blind at the start to the possible outcomes.
Related Opinion:
The Sax team concluded
that “up to two-thirds of deaths in current smokers can be attributed to
smoking. Cessation reduces mortality …the earlier in life [the] greater [the]
reduction”.
For those with an
epidemiological bent, the study authors argue that smoking in Australia
manifests characteristics of a mature epidemic.
A mature epidemic is
rather like a volcano on heavy doses of diazepam: low rate of current smoking;
long duration and stable intensity of smoking among those who smoke; young and
stable age of commencement; high prevalence of past smoking; and similar levels
of relative risk from smoking in successive birth cohorts.
A mature epidemic of
tobacco use is not a picnic ground any more than the side of a seemingly
quiescent volcano. People who live near tobacco still die. And don’t kid
yourself that it will never blow.
Related Feature:
Yes, we have made
immense gains in tobacco control. Most people who quit smoking we know do so on
their own — impressed, I imagine, by the overwhelming evidence about its harm.
But quitting becomes easier if society does not tell people attractive lies about
tobacco. Thank goodness we no longer advertise tobacco and so diminish the risk
of seduction and deception.
But every smoker who
can be urged and helped to quit smoking, when seen in general practice for
example, is potentially a life saved.
They are saved not
only from death but also from a huge amount of suffering, and studies such as
45 and Up confirm that if you quit, the results are good.
Professor Leeder is an emeritus professor of
public health and community medicine at the Menzies Centre for Health Policy at
the University of Sydney. He is also editor-in-chief of the Medical Journal of Australia.
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