In a recent study published in JAMA Network Open, researchers quantified the association between cigarette smoking and all-cause and cause-specific deaths by sex, ethnicity, and race.
Studies have reported considerable variations in smoking habits and SC (smoking cessation) patterns among socioeconomic groups with differing demographics in the United States (US); however, data on cigarette smoking hazards and SC benefits among demographically diverse individuals are lacking. The availability of scientific literature could guide policy-making and motivate individuals to quit smoking, thereby improving their quality of life.
About the study
In the present national-level prospective cohort study, researchers assessed the relationship between smoking and all-cause and cause-specific death rates by sex, race, and ethnicity to determine the detrimental effects of smoking and the beneficial effects of CS on overall survival.
The team utilized publicly available data of civilians and non-institutionalized individuals from the annually conducted national-level US health interview surveys obtained from January 1997 to December 2018 through questionnaires filled out by 551,388 25-year to 84-year individuals at enrollment. The data obtained were linked to the National Death Index, and follow-up assessments were performed for all-cause and specific-cause deaths through 31 December 2019.
The study exposures were the status of smoking at enrollment, age at SC, and years elapsed since SC, as reported by the study participants. The prime study outcomes were specific cause deaths from cardiovascular (CVS) disorders, lower respiratory tract disorders, and cancer, and all-cause deaths. Cox proportional hazards regression modeling was used for calculating the adjusted death rate ratios (RR) comparing former, current, and never smokers. Weighted average analyses were performed by sex, ethnicity, and race.
Data adjustments were performed for alcohol intake, age at risk, and level of education. Individuals were classified as never-smokers if they had not smoked ≥100 cigarettes in their entire life, and those who had smoked ≥100 cigarettes were considered ever smokers. Ever smokers who quit smoking in the last five years of their lives, those who smoked daily or occasionally were classified as current smokers, and smokers who quit smoking by enrollment were categorized as former smokers.
The average age of the study participants was 49 years and most of them (56%, n=307,601) were females. About 16% (n=87,207), 14% (n=75,545), 65% (n=355,782), and six percent (n=32,854) individuals were Hispanics, non-Hispanic (NH) Blacks, NH Whites, and belonged to other NH ethnicities, respectively.
Current cigarette smoking prevalence ranged between 10% in Hispanic females and 26% in Black males. Among current smokers, non-daily smoking was most commonly reported among Hispanics (males, 40% and females 33%) and was least commonly reported among Whites (16% for males and females). Across ethnicities and races, men commenced smoking at a lower age and smoked a higher number of cigarettes daily than women.
In total, 74,870 individuals aged between 25 years and 89 years died, of which, 49% (n=36,79) and 51% (n=38,078) were males and females, respectively. An RR value of 2.8 was observed for all-cause deaths among current smokers versus never smokers. Individuals who quit smoking showed significantly lesser death rates than current smokers.
Compared to never-smokers, the RR values for SC before 35 years of age, at 35 years to 44 years of age, at 45 to 54 years of age, and 55 to 64 years of age were 1.0, 1.2, 1.5, and 1.7, respectively. Likewise, compared to never-smokers, the RR values for individuals who quit smoking five to 14 years before enrollment, 15 to 24 years, 25 to 34 years, and ≥35 years before enrollment were 1.7, 1.4, 1.2 and 1.0, respectively.
The relative excess deaths associated with current smoking were usually comparable in males and females, with RR values of 2.7 and 2.9, respectively. Similar patterns were observed after SC benefits were analyzed by age and duration. The RR values by sex were comparable but differed by ethnicity and race. RR values for Hispanics, NH Blacks, NH Whites, and other NH ethnicities and races were 2.0, 2.2, 3.0, and 2.2, respectively.
A comparison of individuals who gave up smoking before 45 years of age with those who never smoked yielded all-cause death RRs of 1.2, 1.2, 1.1, and 1.2 were observed among Hispanics, NH Blacks, NH Whites, and other NH individuals, respectively. Classifying individuals who quit smoking in the last five years of death as former smokers (rather than current smokers) was primarily limited to those who quit smoking at advanced ages.
Limiting the analysis to individuals with no history of chronic illnesses at enrollment, the former versus never all-cause death RRs were lowered further. Associations between never-smokers and former or current smokers were comparable when stratified by the duration of follow-up. Performing ethnicity- and race-specific analyses for fitness (or physical activity) yielded similar associations as the main analysis.
Additionally, analyses among current regular smokers categorized by the smoking initiation age and the smoked amount indicated that RR values for lower versus higher smoking exposure would be comparable across groups if smoking habits were identical across ethnic and racial groups.
Overall, the study findings showed that among males and females from diverse ethnic and racial groups, current smokers showed ≥2.0-fold greater all-cause death rates than individuals who never smoked.
- Thomson, B. et al. (2022) "Association Between Smoking, Smoking Cessation, and Mortality by Race, Ethnicity, and Sex Among US Adults", JAMA Network Open, 5(10), p. e2231480. doi: 10.1001/jamanetworkopen.2022.31480.