Vascular Benefits of Stopping Smoking Are Rapid

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Vascular Benefits of Stopping Smoking Are Rapid CME

News Author: NainggolanCME Author: Vega, MD

From Heartwire — a professional news service of WebMD

May 8, 2008 — People who quit smoking will see a rapid decline in the risk of death from coronary heart disease (CHD) and other vascular disorders, a new analysis of the Nurses' Health Study shows [1]. And although the study participants were all women, lead author Dr Stacey Kenfield (Harvard Medical School, Boston, MA) told heartwire: "We feel that we can generalize our findings to men who have a similar smoking profile."

Kenfield and colleagues report their findings in the May 7, 2008 issue of the Journal of the American Medical Association. They found that 61% of the full benefit of quitting in regard to CHD mortality and 42% of the full benefit of quitting in regard to cerebrovascular deaths was realized within the first five years of stopping smoking.

"The harms of smoking are reversible, but for some causes of death, the reduction takes many years, so it's never too early to quit smoking. On the other hand, for some diseases — eg, CHD — there is a rapid decline in risk, so it's never too late to stop smoking, even if you've been smoking for many, many years," Kenfield noted.

First few cigarettes a day account for vascular disease risk

In their analysis, the researchers have included an additional 16 years of follow-up from the original Nurses' Health Study cohort report, including a total of 12,483 deaths, and updated estimates for total mortality, further categorized into CHD, cerebrovascular disease, respiratory disease, chronic obstructive pulmonary disease (COPD), a range of cancers, and other causes.

They point out that the smoking status of participants was updated every two years, enabling a more accurate evaluation of the detrimental effects from long-term smoking and the risk reduction over time from sustained cessation. Other studies — which have not updated smoking exposure over time or used smoking information just before diagnoses — may obscure the harms of continuing to smoke and the benefits of cessation, they note, "because current smokers may quit smoking over time and some past smokers may resume smoking."

Participants were classified as never, past, or current smokers, with current smokers split into categories of one to 14 cigarettes per day, 15 to 24, 25 to 34, and 35 or more.

The relationship between an increasing risk of death with increasing numbers of cigarettes smoked per day varied by disease outcome — the trend was less pronounced for vascular disease, suggesting that the first few cigarettes account for most of the increased risk; in contrast, an increased number of cigarettes smoked per day substantially increased the risk of death from respiratory disease.

Vascular disease mortality by number of cigarettes smoked per day among 104,519 women in the Nurses' Health Study followed up from 1980 to 2004a

Never smoker

Past smoker

Current smoker

Current smoker, 1 - 14 cigarettes smoked per day

Current smoker, 15 - 24 cigarettes smoked per day

Current smoker, 25 - 34 cigarettes smoked per day

Current smoker, ≥35 cigarettes smoked per day

p for trend

Total vascular disease deaths, nb (n = 2957)

1073

977

907

261

396

163

87

Multivariate HRc

1 (reference)

1.32

3.26

2.66

3.53

3.73

3.73

<0.001 a. All covariates, including smoking, updated until diagnosis of disease b. Includes CHD and cerebrovascular diseasec. Hazard ratio (HR) adjusted for age, follow-up period, history of hypertension, diabetes, high cholesterol, body-mass index, change in weight from age 18 to baseline (1980), alcohol intake, physical activity, previous use of oral contraceptives, postmenopausal estrogen therapy use and menopausal status, parental history of myocardial infarction (MI) at age 65 years or younger, cigarettes smoked per day during the period prior to quitting, and age at starting smoking

Smokers were also categorized with regard to the age at which they started smoking: 17 years or younger, 18 to 21, 22 to 25, and 26 years or older. For vascular disease, the age of starting smoking seemed to play less of a role in determining the risk of death than it did for respiratory disease, lung cancer, and other smoking-related cancer mortality.

Vascular disease mortality by age at starting smoking among 79,172 current smokers in the Nurses' Health Study followed up from 1980 to 2004a

Never smoker

Starting age ≤17

Starting age 18 - 21

Starting age 22 - 25

Starting age >26

p for trend

Total vascular disease deaths, nb (n = 2957)

1073

190

517

133

67

Multivariate HRc

1 (reference)

3.61

3.15

3.49

3.44

0.84 a. All covariates, including smoking, updated until diagnosis of disease b. Includes CHD and cerebrovascular disease c. Adjusted for age, follow-up period, history of hypertension, diabetes, high cholesterol, body-mass index, change in weight from age 18 to baseline (1980), alcohol intake, physical activity, previous use of oral contraceptives, postmenopausal estrogen therapy use and menopausal status, parental history of MI at age 65 years or younger, cigarettes smoked per day during the period prior to quitting, and age at starting smoking

Rapid decline in vascular death risk in first five years after quitting

For the cessation analysis, past smokers were classified into categories of time since quitting: less than five years, five to less than 10 years, 10 to less than 15 years, 15 to less than 20 years, and 20 or more years.

A more rapid decline in risk after quitting smoking compared with continuing to smoke was observed in the first five years for vascular diseases compared with other causes: 61% of the full benefit of quitting with regard to CHD death and 42% of the benefit of quitting with regard to cerebrovascular death was realized within five years of stopping smoking.

In contrast, it took much longer for the excess mortality risk associated with respiratory disease and smoking-related cancers to approach that of a never smoker: 20 years for COPD and 30 years for lung cancer.

"I think it is encouraging that for all smoking-related cancers and other cancers, former smoker's risks reach never smoker's risks at 20 years or after 20 years," Dr. Kenfield commented. "Also, we found a 58% increase in risk of dying from other cancers that are not thought to be associated with smoking. One of these was colorectal cancer (current smokers had a 63% increased risk of dying and former smokers had a 23% increased risk of dying, compared to nonsmokers). There could be other cancers associated with smoking, but we had too few deaths to evaluate other types of cancer. Hopefully this can be addressed in the future with more follow-up".

Vascular disease mortality by time since quitting smoking among 104,519 women in the Nurses' Health Study followed up from 1980 to 2004a

Current smoker

Never smoker

Former smokers, years since quitting ≤5

Former smokers, years since quitting 5 to <10

Former smokers, years since quitting 10 to <15

Former smokers, years since quitting 15 to <20

Former smokers, years since quitting ≥20

p

Total CHD deaths, n (n = 1385)

473

492

81

59

64

59

157

Multivariate HRb

1 (reference)

0.26

0.53

0.40

0.43

0.36

0.23

<0.001

Total CVD deaths, nc (n = 734)

213

277

45

30

31

35

103

Multivariate HRb

1 (reference)

0.36

0.73

0.50

0.51

0.52

0.36

<0.001

Total vascular disease deaths, nc (n = 2957)

907

1073

193

141

139

128

376

Multivariate HRb

1 (reference)

0.31

0.69

0.52

0.51

0.43

0.30

<0.001 a. All covariates including smoking updated until diagnosis of diseaseb. Adjusted for age, follow-up period, history of hypertension, diabetes, high cholesterol, body-mass index, change in weight from age 18 to baseline (1980), alcohol intake, physical activity, previous use of oral contraceptives, postmenopausal estrogen therapy use and menopausal status, parental history of MI at age 65 years or younger, cigarettes smoked per day during the period prior to quitting, and age at starting smokingc. Cardiovascular disease (CVD) Includes CHD and cerebrovascular disease

Kenfield concluded: "We want current smokers to stop smoking, and if we can't prevent people from starting to smoke at all, we at least need to postpone the age at which they start. Other studies show the earlier someone starts smoking, the higher his or her chances are of becoming a regular smoker and the less likely he or she is to quit."

Source

Kenfield SA, Stampfer MJ, Rosner BA, et al. Smoking and Smoking Cessation in Relation to Mortality in Women. JAMA. 2008; 299:2037-2047.

The complete contents of Heartwire, a professional news service of WebMD, can be found at www.theheart.org, a Web site for cardiovascular healthcare professionals.

Learning Objectives for This Educational ActivityUpon completion of this activity, participants will be able to:

Describe results of a previous report from the Nurses' Health Study regarding the effects of smoking on mortality. Identify the effect of smoking on the risk of mortality associated with different forms of cancer.

Clinical Context

Smoking is clearly linked with an increased risk of mortality, and a previous report on the Nurses' Health Study by Kawachi and colleagues, published in the November 15, 1993, issue of ls of Internal Medicine, described this risk in detail. Researchers demonstrated that the overall risk of mortality among smokers vs never smokers was 1.87, and the risk of former smokers vs never smokers was significantly elevated at 1.29. Participants who initiated smoking before the age of 15 years had the highest risks for total mortality and cardiovascular disease mortality, but these risks were attenuated to levels similar to never smokers after 10 to 14 years of abstinence from smoking.

The current report from the Nurses' Health Study provides greater detail with regard to cancer mortality risks associated with cigarette smoking in women.

Study Highlights

The Nurses' Health Study began following 121,700 female nurses in the United States in 1976. Subjects have provided health information every 2 years since initiation of the study, including data regarding cigarette use. Women with a prior history of cancer were excluded from the current study. In the current study, researchers focused on reports of overall mortality as well as specific cancer, vascular, and respiratory causes of mortality from 1980 forward. Never smokers were used as the reference group, and the risk of study outcomes associated with smoking was adjusted for body mass index as well as disease and lifestyle factors. In 1980, 28% of the study cohort reported current smoking, and 26% were former smokers. The mean age at smoking initiation was 19 years. Current smokers had lower body mass index values and slightly less hypertension and also exercised less compared with never or former smokers. 12,483 deaths occurred in the study group, 28.9% and 35.2% of which occurred among current and former smokers, respectively. Only 8% of subjects alive in 2002 were current smokers. Current smokers experienced a HR of 2.81 for total mortality compared with never smokers, and they were also at higher risk for all major cause-specific mortality. Current smokers had a higher risk of death associated with all smoking-related cancers vs never smokers. These cancer sites included bladder, cervix, esophagus, lip and mouth, pharynx, pancreas, and stomach. Smokers were also at higher risk of mortality resulting from acute myeloid leukemia. Current smokers also had a significant increased risk of mortality resulting from colorectal cancer vs never smokers (HR = 1.63), but the effect of current smoking on the risk of ovarian cancer mortality was not significant. These same trends were evident among former smokers. Overall, 64% of deaths among current smokers were attributable to cigarette smoking. Earlier initiation of smoking was associated with a higher risk of death, particularly for death related to respiratory disease or cancer. The risk of death decreased by 13% within 5 years of quitting cigarettes, and this risk was further attenuated to levels comparable with never smokers at 20 years after quitting. The risk of death resulting from vascular disease declined more rapidly compared with other mortality risks following smoking cessation, with 61% of the full potential benefit for coronary heart disease mortality accrued in the first 5 years after quitting. Approximately 28% of deaths among former smokers were attributable to cigarette smoking.

Pearls for Practice

A previous report from the Nurses' Health Study demonstrated that both current and former smokers had an increased risk of mortality compared with never smokers, but this risk was significantly attenuated after 10 to 14 years of abstinence from smoking. Women who began smoking prior to 15 years of age experienced the highest risk of mortality. In the current study, smoking increased the risk of death due to cancers of the cervix, colon and rectum, and stomach. However, the risk of ovarian cancer mortality was not significantly increased with smoking.

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