Wednesday June 9 2010
Stopping smoking reduces your risk of having a heart attack
“Heart attack hospital admissions have fallen since the smoking ban,” reported The Times. This news is based on a study on the rates of hospital admissions for heart attacks before and after the smoking ban was introduced in England on July 1 2007. Researchers estimated a 2.4% reduction in heart attack emergency admissions to hospital (or 1,200 fewer admissions) in the 12 months following the ban.
This well-conducted study shows a clear association between the smoking ban and a decreased rate of hospital admissions for heart attack. As the study did not look at smoking status or people’s exposure to second-hand smoke before the ban, it is not possible to say how much of the decline is due to less exposure to second-hand smoke and how much is due to people giving up smoking. Further research that assesses the ban’s long-term impact and its effect on other diseases is warranted.
The risks associated with smoking and heart disease, heart attack and cancer are well known. In addition to smoking, there are other risk factors for heart attacks, such as not getting enough exercise, being overweight and having high blood pressure and cholesterol levels. The risk of a heart attack can be lowered by adopting a healthy lifestyle and diet.
Where did the story come from?
The study was carried out by researchers from the University of Bath. It was funded by the Department of Health’s Policy Research Programme. The study was published in the peer-reviewed British Medical Journal.
What kind of research was this?
This time trend study looked at whether there was a difference between the number of people admitted to hospital with a heart attack in the five years before the smoking ban began in England compared to the 15 months afterwards.
The researchers wanted to assess the short-term effects of the smoking ban. Further longer-term studies are likely to follow this work.
What did the research involve?
Data for the analysis were obtained from hospital statistics collected on all patients receiving care from the NHS in England. The researchers were interested in the number of emergency admissions for heart attack between July 1 2002 and September 30 2008. The smoking ban came into effect on July 1 2007.
To assess whether there was a difference in the weekly rate of emergency admissions for heart attack before and after the ban, the researchers developed a statistical test called a ‘segmented Poisson regression model’. This analysis took into account factors that can affect the rates of heart attack, such as changes in temperature, flu rates, the week of the year and the Christmas holidays. Factoring these in was important as admissions for heart attack can vary seasonally in England from a low in August to a high in January.
To explore the impact of the smoking ban in different population subgroups, the researchers grouped the data by gender and age (whether the patient was younger or older than 60).
Data on heart attack admissions before the smoking ban were used to predict the rates of heart attacks between July 1 2007 and September 30 2008 had the law not been passed. This figure was then compared to data of the actual rates of heart attacks in the 15 months after the smoking ban. The two figures were used to estimate the number of hospital admissions for heart attacks that were prevented as a result of the smoking ban in the first year of implementation.
What were the basic results?
Overall, between 2000 and 2008 there was a decrease in the number of emergency admissions for heart attack. This decrease was accelerated from around 2002 and was greater in older than younger age groups.
There was a seasonal pattern of heart attacks, with emergency admissions peaking over Christmas and early spring, and lower admission rates in summer. Most occurred in men and those over 60 years, with relatively few events in women under 60 years.
After the smoking ban came into effect there was a drop of 2.4% in the number of emergency admissions for heart attack. From this the researchers estimated that just over 1,200 emergency admissions for heart attack were prevented over a 12-month period.
In men and women aged 60 or older, there was a reduction of 3.07% and 3.82%, respectively, and men under 60 had a drop in admissions of 3.46%. Emergency admissions for younger women also dropped by 2.46%, but this was not statistically significant (and therefore is more likely to be a chance finding).
How did the researchers interpret the results?
The researchers say that hospital admissions for heart attacks reduced after the introduction of the smoking ban.
They say the reductions they saw were smaller in England than in other jurisdictions, such as Scotland. They suggest that this may be because exposure to second-hand smoke in England was reduced in the run-up to the smoking ban, with many public places and workplaces already smoke-free. They also say that their study may have adjusted more than previous studies for other factors that could lead to heart attacks.
This study showed that the rates of hospital heart attacks have been falling since 2000, and that since the smoking ban the rates have fallen by an estimated additional 2.4%. The researchers suggest that this may be due to the general population being exposed to less second-hand smoke since the legislation came in.
They suggest that the reduction in heart attack admissions may not be as high as in other countries, because many public places in England were already smoke-free before the ban came into force. Other studies have suggested that almost 55% of employed adults in England already worked in a smoke-free environment before the ban.
Overall, this well-conducted research shows a clear association between the smoking ban and a decreased rate of hospital admissions. As the study did not look at smoking status or people’s exposure to second-hand smoke before the ban, it is not possible to say how much of the decline is due to less exposure to second-hand smoke and how much is due to people giving up smoking. It would also be useful to have an assessment of how frequently individuals were exposed to smoke (if they were non-smokers) before the ban, for example if they were bar workers or worked in other smoky environments.
As this research was conducted over the short term, further studies are required to assess the long-term impact of the smoking ban. In addition to smoking there are other risk factors for heart attack, such as lack of exercise, being overweight and high blood pressure and cholesterol levels. The risks of heart attack can be lowered by adopting a healthy lifestyle.