Stopping Smoking Earlier in Life Reduces More Risks

People who stop smoking by age 35 reduce almost 100% of the extra risk they had of dying from cancer or any other cause.

Researcher: Farhad Islami, MD, PhD
Institution: American Cancer Society, Department of Surveillance and Health Equity Science
Area of Focus: Cancer Disparity Research

The Challenge: Smoking is still the major reason people die from cancer. Research has shown that people who start smoking when they are younger have a greater risk of dying than those who start later.

Quitting smoking (especially at younger ages) greatly reduces that risk. Nevertheless, there are still 34 million adults in the United States who still smoke cigarettes.

Statistics about how the age people are when they start and quit smoking affects their risk of death need to be updated for a contemporary population in the US. A specific gap in the current knowledge has been population-specific evidence on the benefits of quitting smoking among groups historically under-represented in medical research.

Research has shown that the patterns of smoking and smoking cessation differ markedly among people in different demographic groups. But there has been little research done to quantify the race-, ethnicity-, and sex-specific links of smoking with death.

The Research: Farhad Islami, MD, PhD, the senior scientific director of Cancer Disparity Research at the American Cancer Society (ACS), was the senior author of 2 recent studies. The first, in JAMA Oncology, reviewed data to get more current information about how the age people start and stop smoking is linked with the risk of dying from cancer. The second, in JAMA Network Open, looked at differences in smoking based on race, ethnicity, and sex and the risk of dying from any cause, including cancer.

For each study, the research team used data from the US National Health Interview Survey and the National Death Index, but age ranges and years studied varied between the two. In each case, there were more than 400,000 participants who were followed for an average of 10 or 11 years. The combined age ranges for the studies were between the ages of 25 and 84.

Age

Islami and his fellow researchers found that people who were currently smoking were 3 times more likely to die from cancer compared to those who never smoked.

They also found that smoking would account for:

• 75% of deaths from cancer among those who started smoking when they were younger than age 10
• 59% of deaths from cancer among those who started smoking when they were age 21 or older

More broadly, Islami and his team reported that among people who were currently smoking, about 70% of deaths from cancer, 60% of deaths from heart disease, and more than 90% of deaths from lower respiratory disease were attributable to smoking.

People who quit smoking between the ages of:

• 15 to 34 avoided about 100% of the extra risk of dying from cancer they would have had if they’d continued to smoke
• 35 to 44 avoided about 89% to 90% of the extra risk of dying from cancer they would have had if they’d continued to smoke
• 45 to 54 avoided about 78% of the extra risk of dying from cancer they would have had if they’d continued to smoke
• 55 to 64 avoided about 56% of the extra risk of dying from cancer they would have had if they’d continued to smoke
  

These results show that stopping smoking, even at an older age, greatly reverses the risk of dying from cancer. People who delayed smoking until they were adults had a greatly reduced risk of dying from cancer compared to those who started smoking at a younger age. Still, those who started smoking at age 21 and older had 2 times the risk of dying from cancer compared with those who never smoked.

Race/Ethnicity and Sex

The researchers also found that compared with people who never smoked, people who currently smoked had different risks of death based on their race and ethnic group.

• White people who smoked were 3 times more likely to die than White people who never smoked.
• Black people, Hispanic, and other non-Hispanic groups were 2 times more likely to die than people who never smoked.
• 31% of all deaths among White men and 22% of all deaths among White women were attributable to smoking.
• 27% of all deaths among Black men and 19% of all deaths among Black women were attributable to smoking.
• 20% of all deaths among Hispanic men and 11% of all deaths among Hispanic women were attributable to smoking.
  

The researchers note that the relatively lower risk of dying among Black and Hispanic groups was likely because, compared to White people, they smoked fewer cigarettes a day on average, were less likely to smoke every day, and began smoking at slightly older ages .

The benefits of quitting, however, were consistent among men and women from diverse racial and ethnic groups, particularly among those who quit smoking before age 45.

Islami was helped by Ahmedin Jemal, DVM, PhD, and former ACS Surveillance & Health Equity Science team member, Blake Thomson, DPhil, who led both papers when working at the ACS. Islami and Thomson collaborated with scientists from the University of Oxford in the United Kingdom.

Why Does it Matter? The findings from this study show once again that starting to smoke at any age is “extremely hazardous.” But they also show that the younger someone is when they quit smoking, the more they can lower their risk of dying from cancer or any other cause.

The problem is that recent progress in increasing the percentage of people who quit smoking in the US has been modest.

The researchers conclude, “broad and equitable tobacco cessation support for individuals who currently smoke, coupled with tobacco control policies that prevent the next generation from starting to smoke, may avert considerable premature smoking-related mortality in the coming decades if successful.”

Having specific information about the links between age-, race-, ethnicity-, and sex-specific links with smoking and death allows for health policy planning and for providing targeted messages, especially for groups historically underrepresented in medical research. And such personalized efforts may better motivate population-specific groups to quit smoking.