Smokers shouldn’t wait until they develop cardiovascular disease (CVD) to consider ditching their habit—current smokers are far more likely to suffer a fatal event, such as major heart attack or stroke, as their first CVD event compared to people who don’t smoke, according to findings published in the Journal of the American Heart Association.
Despite a dramatic increase in public awareness of the dangers inherent with smoking tobacco, about 34 million adults in the U.S. still report cigarette use. However, while years of research have demonstrated a consistent link between cigarette use and various adverse CVD and non-CVD outcomes, “few studies have evaluated the long- term morbidity and mortality attributed to CVD subtypes while adjusting for competing risk of non-CVD deaths, which is necessary as smoking is associated with an increased risk of multiple outcomes simultaneously,” study author Sadiya S. Khan, MD, MSc, of Northwestern University Feinberg School of Medicine in Chicago, and colleagues explained.
What’s more, they added, creating a competing-risk framework would allow for better understanding of “the comparative risk of the first presentation of CVD being a fatal or non-fatal event as well as elucidating which of the different CVD subtypes are more likely to occur first.”
In order to better characterize these risks, Khan and colleagues pooled and harmonized individual-level data from nine population-based cohorts to examine the association between smoking status and total CVD, as well as CVD subtypes, including fatal and non-fatal coronary heart disease (CHD), stroke, congestive heart failure (HF), and other CVD-related deaths.
Their analysis found “an increased risk of CVD across all subtypes, in particular on the occurrence of a fatal CVD event as first presentation of CVD, in those who reported smoking compared with those who did not. Those who reported smoking had, on average, earlier onset of CVD and shorter overall survival across the life course.”
In an accompanying press release from the American Heart Association (AHA), Kahn explained that there is usually “more awareness and concern about cancer as a result of smoking than heart disease, so we wanted to better define the risks of smoking related to different types of cardiovascular disease and, most importantly, to cardiovascular death.”
A recent study published in the AHA journal Stroke highlights the disparity between smoking cessation efforts among cancer patients and cardiovascular conditions—according to the analysis by Parikh and colleagues, the smoking quit ratio was 71.3% among patients who had survived cancer versus 60.8% for stroke survivors.
“Our findings note that preventing a heart attack, stroke, or heart failure is vital, yet preventing unexpected sudden death as the first manifestation of cardiovascular disease is clearly a priority. People who smoke may not realize the harm cigarettes are causing their body until it’s too late,” Khan added. “Another notable finding among people who smoked was the early onset of CVD, and among those who developed CVD, how much younger they were. There’s not a lot of research on young adults who smoke, particularly among young men. Our study adds important perspective.”
For their analysis, Khan and colleagues pulled data from nine cohorts—they used data from one examination for each cohort from participants who had available information on self-reported smoking status, covariates, and at least 10 years of follow-up.
The study included a total of 1,949,658 person-years of follow-up consisting of observations made from 1948 through 2017. Participants were stratified by sex, index age groups (20-39 years for young adults; 40-59 years for middle-aged adults; 60-79 years for older adults), and smoking status at the index examination. Long-term risk was calculated using a modified Kaplan-Meier analysis, “which accounts for non-CVD death as a competing risk… [and] accounts for fatal non-CVD events as a separate end point rather than a censoring event,” they explained.
A total of 106,165 individuals were included in the pooled cohort; of these, 17,205 (16.2%) were Black and 53,527 (50.4%) were women.
Among the findings:
- The unadjusted event rates for CVD and non-CVD death were higher in those who reported smoking compared to those who did not in all adults, male or female, across all age groups; competing cumulative risks for both non-CVD death and total CVD events were higher among smokers versus non-smokers in all adults; and the long-term risk of non-CVD death and CVD were higher in individuals who reported smoking.
- Middle-aged men had the largest absolute difference in long-term CVD risk between those who smoked (46%) and those who did not (36%); young men had the largest absolute difference in long-term risk for HF between smokers (12%) and non-smokers (5%); the most common CVD subtype was myocardial infarction (MI) and was again more common among smokers than non-smokers.
- Across all sex and age groups, overall survival was significantly shorter among baseline smokers than non-smokers, which the authors noted was attributable to the significantly lower number of years lived free of CVD. “For example,” they wrote, “among middle-aged men, overall survival was significantly higher in those who reported not smoking (32.6 years) compared with those who reported smoking (27.1 years) at baseline, leading to a significantly higher number of years lived free of CVD (29.1 versus 24.0 years), indicating a delay in CVD onset by 5.1 years.”
Strikingly, the hazard ratio (HR) for first CVD presentation as a fatal event was dramatically higher across all sex and age groups for smokers versus non-smokers, with the most dramatic increase occurring among young adults:
- HR for fatal first CVD presentation in men: 2.38 (2.05-2.75) for young adults aged 20-39 years; 1.79 (1.68-1.92) for middle-aged adults aged 40-59 years; 1.38 (1.27-1.51) for older adults aged 60-79 years.
- HR for fatal first CVD presentation in women: 2.01 (1.62-2.49) for young adults; 1.82 (1.68-1.98) for middle-aged adults; 1.30 (1.17-1.43) for older adults.
And, while smokers in all age groups also faced increased risk for a first non-fatal CVD events compared to non-smokers, the risk for a fatal event was substantially higher in most cases—the only exception was for older women, whose risk for a non-fatal CVD event was 5% higher than a fatal event (HR 1.35 versus 1.30).
“These results offer a very compelling message that people who smoke need to hear—smoking can kill you before you even know you have cardiovascular disease. It can, indeed, be a silent killer,” said Esa M. Davis, MD, a member of the AHA’s Council on Lifestyle and Cardiometabolic Health, associate professor of medicine and the clinical and translational science medical director of the tobacco treatment service of the University of Pittsburgh Medical Center, who was not involved in the study, in the AHA press release. “Heart attacks, strokes, and other types of cardiovascular disease don’t always have early symptoms, so if you don’t know you have CVD, it can’t be treated. You can help prevent CVD by never smoking or stopping smoking as soon as possible.”
Study limitations included a lack of data on smoking intensity; the authors’ decision to classify those who smoked but quit over one year ago as not smoking at baseline may underestimate the true risk of CVD morbidity and mortality; using baseline risk factor levels, which does not account for change over time; and the long-term data used lead to the inclusion of older data that may be biased by changes in secular trends, such as declines in smoking prevalence over time.
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Current smokers were much more likely than non-smokers to suffer both cardiovascular disease (CVD)-related and non-CVD events, and their first presentation of CVD was substantially more likely to be fatal, across all sex and age groups, according to a pooled analysis of data from nine population-based cohorts in the U.S.
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In this study, those who reported smoking had, on average, earlier onset of CVD and shorter overall survival across the life course.
John McKenna, Associate Editor, BreakingMED™
The study was funded by NIH and the National Heart, Lung, and Blood Institute.
Coauthor Berry reported personal fees from Astra Zeneca, personal fees from the Cooper Institute, grants from Abbott, and grants and personal fees from Roche outside the submitted work. Coauthor Allen reports grants from the National Institutes of Health and grants from the American Heart Association outside the submitted work.
Cat ID: 358
Topic ID: 74,358,730,358,143,489,925
