Quitting smoking for 3 years improves heart disease prognosis
MedWire News: Quitting cigarette smoking for at least 3 years is associated with important improvements in exercise parameters that predict cardiovascular disease (CVD) risk, US research shows.
The study, conducted by James Stein and colleagues from the University of Wisconsin in Madison, evaluated the long-term effects of smoking cessation and continued smoking on treadmill stress testing (TST) parameters.
Stein explained to MedWire News: "The effects of smoking and smoking cessation on stress testing and exercise markers of CVD risk have not been studied longitudinally in a large, prospective cohort of contemporary smokers. This is a matter of considerable importance because contemporary smokers are more overweight than those studied previously, and smoking cessation is associated with weight gain, which can adversely affect exercise capacity. Furthermore, the long-term effects of smoking cessation on exercise physiology are unclear."
The researchers therefore performed TST in 600 current smokers (mean age 43.4 years; 61% women) before and 3 years after their target smoking cessation date.
TST assesses exercise capacity, peak heart rate (HR) increase, rate-pressure product (RPP; peak HR x peak systolic blood pressure [BP]), percent HR reserve (maximum HR/[220-age]), and 60-second HR recovery, all of which are predictive of future CVD events and mortality, the researchers explain.
At each stage of exercise, including peak exercise and 1 minute after exercise cessation, HR, BP, and estimated work load in metabolic equivalents (METs; 1 MET = 3.5 ml O2 uptake/kg body weight per minute) were determined. After achieving the maximum workload, participants performed a minimum 3-minute cool-down at walking speed.
At baseline, the study participants smoked a mean of 20.7 cigarettes per day. Their exercise capacity was 8.7 METs, HR reserve was 86.6%, HR increase was 81.1 beats per minute, and HR recovery was 22.3 beats.
At this time point, current smoking (cigarettes per day) and smoking burden (pack-years) were significantly inversely associated with peak MET, peak HR increase, and HR reserve. In addition, exercise peak RPP and HR recovery were inversely associated with smoking burden, but not with current smoking.
After 3 years, 168 (28%) participants had quit smoking. Compared with continuing smokers, abstainers had slightly lower carbon monoxide levels at baseline, but were similar in regard to all other parameters.
Abstainers had significantly greater increases in body mass index and waist circumference than people who continued to smoke.
However, despite their weight gains, successful abstainers had significantly greater improvements than continuing smokers in RPP (difference in improvement of 2,055 mm Hg beats/min), HR increase (5.9 beats/min), and HR reserve (3.7%), even after adjustment for confounding variables such as gender and baseline smoking intensity.
These findings are suggestive of improved cardiovascular prognosis, and indicate that the people who quit smoking are less likely to develop and die of heart disease, said Stein.
This suggests that "improved exercise physiology may be a mechanism for cessation-related reductions in CVD risk," the researchers add in the American Heart Journal.
Stein concluded that quitting smoking is the most important measure a person can take to reduce their risk for CVD.
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By Laura Dean