New research helps former smokers to lower their risk of death

[Sept 28, 2022: NCI Press Office, NIH/National Cancer Institute]

Study suggests that some smokers may have robust mechanisms that protect them from lung cancer. (CREDIT: iStock Photos)

Former smokers who stick to a healthy lifestyle have a lower risk of dying from all causes than those who don’t engage in healthy habits, according to a new study by researchers at the National Cancer Institute (NCI), part of the National Institutes of Health (NIH).

The reduced risk of dying was observed for specific causes, including cancer and heart and lung diseases. Lifestyle interventions have not been robustly studied in former smokers, and these new findings could have important implications for the 52 million former smokers in the United States.

Maintaining a healthy lifestyle—defined as doing things such as being physically active and having a healthy diet—was associated with a 27% reduction in the risk of death over the 19-year follow-up period, compared with not maintaining a healthy lifestyle.

The findings come from an analysis of a large group of former smokers who participated in the NIH-AARP Diet and Health Study.

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“I was surprised to see the robust associations [with lifestyle],” said Maki Inoue-Choi, Ph.D., of the Division of Cancer Epidemiology and Genetics at NCI, lead author of the paper. “Former smokers who adhered to evidence-based recommendations for body weight, diet, physical activity, and alcohol intake had a lower risk of mortality than former smokers who didn't adhere to these recommendations.”

Quitting smoking is well known to have many health benefits, but former smokers still have a higher risk of disease and premature death than people who have never smoked.

Past studies have suggested that people who follow healthy lifestyle recommendations, such as maintaining a healthy body weight, being physically active, eating a healthy diet, and limiting alcohol consumption, may have a lower risk of disease and death. However, few studies have looked at the benefit of such adherence among former smokers.

The current analysis included 159,937 former smokers who had completed questionnaires asking about lifestyle, demographics, and other health-related information between 1995 and 1996 when they joined the NIH-AARP Diet and Health Study.

The participants, whose average age at study entry was 62.6 years, were followed for approximately 19 years. During the follow-up period, which extended through 2019, 86,127 participants died. Death information, including cause of death, came from the National Death Index.

For each participant, the researchers calculated a total adherence score ranging from no adherence to full adherence. The total adherence score incorporated individual scores for body mass index, based on guidelines from the World Health Organization; for dietary quality, based on the Dietary Guidelines for Americans, 2010-2015; for physical activity, based on the second edition of the Physical Activity Guidelines for Americans; and for alcohol use, based on the Dietary Guidelines for Americans, 2020-2025.

Former smokers who had the highest total adherence scores had a 27% lower risk of death from any cause than those with the lowest scores. In addition, participants with the highest scores had a 24% reduction in risk of death from cancer, 28% reduction in risk of death from cardiovascular disease, and 30% reduction in risk of death from respiratory disease.

Age- and Sex-Adjusted Mortality Rate by Total Adherence Score Stratified by Years Since Cessation Among Former Smokers. (CREDIT: JAMA Network)

The reductions in risk of death were observed regardless of health status, other health conditions, how many cigarettes participants used to smoke per day, years since they quit, and age they began smoking.

The researchers also evaluated the benefit from adherence for individual lifestyle recommendations. In each case, people with the highest score had a lower risk of death than those with the lowest score: 17% lower for physical activity, 14% lower for body weight, 9% lower for diet quality, and 4% lower for alcohol intake.

Scoring System of Adherence to the Body Weight, Diet, Alcohol Intake, and Physical Activity Recommendations. (CREDIT: JAMA Network)

“To have the greatest benefit, it is better to adhere to many lifestyle recommendations,” Dr. Inoue-Choi noted. “But even those who adopted just a single lifestyle recommendation experienced benefits.”

The researchers cautioned that studies based on self-reported data can only show associations, not establish cause and effect. Although the researchers controlled for many factors that could have confounded the associations, they said they cannot rule out the possibility that other factors may have affected the associations they observed.

Demographic, Medical, and Smoking Characteristics by Total Adherence Score to the Lifestyle Recommendations Among Former Smokers. (CREDIT: JAMA Network)

The researchers also noted that more studies are needed to explore the associations between adhering to lifestyle recommendations and risk of death among former smokers in more diverse populations.

“The NIH-AARP study is a predominantly White population with relatively high socioeconomic status,” Dr. Inoue-Choi said. “These research questions need to be extended to other populations.”

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Note: Materials provided above by NIH/National Cancer Institute. Content may be edited for style and length.

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