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Heart Risk Falls With Time Since Quitting Smoking in DAD
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17th Conference on Retroviruses and Opportunistic Infections, February 16-19, 2010, San Francisco
Mark Mascolini
Risk of new cardiovascular problems fell as people with HIV put more time between themselves and their smoking history in a large DAD study analysis [1]. But time since quitting did not correlate with a falling risk of death, at least not as the data have been analyzed so far.
Smoking certainly contributes much to cardiovascular risk in Western HIV populations because the nicotine habit remains ingrained in many HIV-infected people--majorities in many places. Smoking independently boosts the risk of death in people with HIV. But does quitting cut that risk?
To find out, Kathy Petoumenos and DAD coworkers studied all DAD participants who reported their smoking status and had no history of heart disease. They tracked people who never smoked plus current and former smokers to figure rates of myocardial infarction (MI), coronary heart disease (CHD, including MI plus invasive coronary artery procedures or death from CHD), cardiovascular disease (CHD plus carotid artery endarterectomy or stroke), and all-cause mortality. For people who quit after joining DAD, the researchers estimated time since they stopped.
The analysis included 8920 people who never smoked, 6265 ex-smokers, 11,951 current smokers, and 8197 people who quit during DAD follow-up. The median age of these people was close to 40, and about 80% were men. Median CD4 counts for all four groups were in the 400s. Median antiretroviral exposure measured about 1.5 years in never-smokers, ex-smokers, and current smokers, compared with 4.1 years in people who quit during follow-up in DAD.
In a multivariate model adjusted for age, gender, calendar year, type of antiretroviral therapy, family history of cardiovascular disease, and time-updated lipid and blood pressure measures, former smokers had a 1.73 times higher risk of myocardial infarction than people who never smoked, while current smokers had a 3.40 times higher risk. Compared with people who never smoked, risk fell stepwise from a high of 3.73 in people who had quit for less than 1 year, to 3.00 for people who had quit for 1 to 2 years, to 2.62 for people who had quit for 2 to 3 years, and to 2.07 for people who had quit for 3 or more years.
Similar patterns held for coronary heart disease and cardiovascular disease, as defined above: Current smokers had a higher risk than former smokers, and the risk decreased with each year since quitting.
But when the DAD team looked at mortality, the pattern crumbled. Former smokers did not run a higher risk of death than people who never smoked, while current smokers had a 28% higher risk (with confidence intervals that did not cross 1). But the stepwise risk deflation with years since quitting did not pertain in this mortality analysis, and confidence intervals for risks starting with 1 year since quitting always crossed 1. Restricting the analysis to people over 50 did not re-establish the earlier pattern of falling risk with longer time since quitting.
Petoumenos and colleagues noted one confounder that they could not iron out in their analysis. People who quit smoking during DAD may have quit precisely because they were sicker than other cohort members and so more likely to die.
Still, the strong tie between more time since quitting cigarettes and ever-declining cardiovascular morbidity adds to the already-compelling rationale to encourage people with HIV to quit and to pursue clinical and behavioral research toward that end.
Reference
1. Petoumenos K, Worm S, Reiss P, et al. Rates of cardiovascular disease following smoking cessation in patients with HIV infection: results from the D:A:D study. 17th Conference on Retroviruses and Opportunistic Infections. February 16-19, 2010. San Francisco. Abstract 124.
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