A new study of deaths from all causes in New South Wales published today in BMC Medicine reports both some very bad and very good news about smoking.
Up until now, Australian estimates of the death and disease risks of smoking have been modelled from large-scale British and United States cohort studies, where researchers followed very large groups of people across many years and compared the death records of “never smokers” with smokers and ex-smokers.
Now, for the first time, we have local cohort data. The 45 and Up study commenced in 2006 and tracked 204,953 people for an average 4.26 years (a total of 874,120 person years).
Researchers recorded participants’ smoking status (when the study started and at various follow-ups) and, where applicable, hospitalisations and death.
Overall, there were 5,593 deaths from all causes, with current smokers nearly three times (2.96) more likely to die than never or former smokers.
The two stand-out results are that up to two-thirds of the deaths in current smokers were due to smoking (the bad news) and that death rates in former smokers who had quit before turning 45 were not different from those in the study who had never smoked (the very welcome news).
As other studies have reported, the smokers in this study died, on average, ten years earlier than the never smokers. With the life expectancy in Australia at 82.1 years, smokers are losing an average of one day in eight off their lives.
So, a person who started smoking at 15, who smoked an average of 15 cigarettes a day and died at 72, would have smoked 312,288 cigarettes in their lifetime. These each take about six minutes to smoke.
Across 57 years of smoking, this translates to 3.56 years of continual smoking, meaning that each cigarette on average can be expected to shave about 2.8 times the time it takes to smoke it off the end of smokers’ lives.
We’ve known for some time that smoking adversely affects almost every body organ and bodily system, from the eyes to the toes.
Big population health data sets now allow us to understand that the list of previous diseases caused and exacerbated by smoking was very conservative. A major US studypublished this month pooled five contemporary US cohort studies including 421,378 men and 532,651 women followed from 2000 to 2011. It found:
17% of the excess mortality among current smokers was due to associations with causes that are not currently established as attributable to smoking.
These associations included deaths from renal failure, hypertensive heart disease, infections, breast and prostate cancer.
When Sir Richard Doll’s 40 year follow-up of his historic British doctors study was published in 1994, the take-home message was “half of all regular cigarette smokers will eventually be killed by their habit”.
We can now say with confidence that up to two-thirds of smokers will die from their smoking, on average ten years early.
Stopping smoking before age 45 appears to eliminate most of this risk.
Only about one in ten smokers do not regret having started, and today there are twice as many ex-smokers than there are daily smokers. Most have quit without any professional or pharmacological assistance.
When American surgeon Sir Wiliam Osler was a medical student in 1919, he was summonsed to see a lung cancer operation, and told that this was a rare disease that he might never see again. He didn’t see another case for 17 years. Then he saw eight in six months – all smokers who had picked up the habit in WWI.
Today, lung cancer is the biggest case of cancer death is the world. It is an epidemic spread by the tobacco industry, facilitated by government inaction. An article in the journalNature in 2001 forecast that a billion deaths will be caused by tobacco this century.
Nations that have taken tobacco control seriously, such as Australia, Canada, Britain and the United States, are leading the way in dramatically reducing smoking rates. This new data will strengthen that resolve.
This article was originally published on The Conversation.
About the author:
Simon Chapman is a Professor of Public Health at Sydney University.