It’s never too late to quit smoking

By Lilian Anekwe

BMJ Group News

What do we know already?

There’s lots of evidence to show that cigarette smoking increases your risk of dying earlier from any cause, or your risk of dying from certain illnesses including cancer, heart disease, chronic obstructive pulmonary disease (COPD), or a stroke.

But few studies have calculated the difference that stopping smoking has on people’s overall length of life, and their risk of dying from different diseases.

We also know a lot less about whether stopping smoking earlier in life makes a difference to how long you live, and what the risk is compared to people who either never smoked or continued smoking.

Researchers looked at this by studying the health records of 19,705 men who were enrolled in a US-based study called the Physicians’ Health Study between 1982 and 1984.

The men filled in questionnaires recording whether they smoked, how long they had smoked and how many cigarettes they smoked a day. If they quit smoking in the five years after the study began, then the researchers noted the age at which they stopped.

Over the following 22 years, the researchers recorded how many men in the study died and collected information about the cause of their death. From this they were able to calculate the effect of quitting smoking on people’s risk of dying.

What does the new study say?

There were a total of 5,594 deaths during the follow-up period. The researchers calculated that 12 people who never smoked died for every 1,000 people included in the study for one year. But 17 people who had smoked in the past died for every 1,000 people included in the study for one year, and 26 people who were current smokers died for every 1,000 people included in the study for one year.

Compared with current smokers, people who quit smoking were 40 percent less likely to die within 10 years and 52 percent less likely to die within 20 years of quitting. This was nearly the same risk as people who had never smoked.

People who quit smoking after age 50 were 46 percent less likely to die during the 22 years that the study lasted than current smokers. Quitting smoking after age 60 reduced the risk of dying during the study by 39 percent.

Among past smokers, the risks of dying from a stroke, heart attack, or colorectal cancer fell to the same as people who had never smoked within 10 years of quitting. But it took 10 years for the risk of dying from smoking-related cancers to fall to the same level as people who had never smoked, 20 years for heart disease, COPD, or lung cancer, and 30 years for prostate cancer.

But only those people who quit before the age of 50 were able to reduce their risk of dying during the study to the same or less risk than someone who had never smoked.