Smoking cessation lowers cardiovascular risk in D:A:D cohort

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HIV-positive smokers had a significantly higher risk of cardiovascular events such as heart attacks and strokes, compared with those who never smoked, but the extra risk declined after quitting and continued to fall with longer time as a non-smoker, according to a study presented this week at the 17th Conference on Retroviruses and Opportunistic Infections (CROI) in San Francisco.

Kathy Petoumenos and colleagues aimed to investigate rates of cardiovascular events and death amongst D:A:D participants who stopped smoking. Past studies have shown that heart disease risk falls within one to two years after smoking cessation in HIV-negative people, and the researchers wanted to see if this would also hold true for people with HIV.

D:A:D (Data Collection on Adverse events of Anti-HIV Drugs) is a large, ongoing observational study comprised of more than 33,000 HIV-positive people seen at more than 200 clinics in Europe, Australia, and the US.

Glossary

cardiovascular

Relating to the heart and blood vessels.

cardiovascular disease

Disease of the heart or blood vessels, such as heart attack (myocardial infarction) and stroke.

myocardial infarction

Heart attack. Myocardial refers to the muscular tissue of the heart. An infarction is the obstruction of the blood supply to an organ or region of tissue.

observational study

A study design in which patients receive routine clinical care and researchers record the outcome. Observational studies can provide useful information but are considered less reliable than experimental studies such as randomised controlled trials. Some examples of observational studies are cohort studies and case-control studies.

coronary heart disease (CHD)

Occurs when the walls of the coronary arteries become narrowed by a gradual fatty build-up. Heart attack and angina are main symptoms.

The D:A:D team divided participants into groups according to smoking status. The largest proportion were current smokers, at 35%; about 25% had never smoked and just under 20% were former smokers. In addition, about one quarter (a total of 8197 individuals) reported that they had quit after entering the study. The researchers did not have enough data to evaluate smokers based on packs smoked per day or number of years smoking.

Most participants (roughly 75%) were men, about half were white, and the average age was just under 40 years. Sex between men was the most common HIV risk factor, but there were more injection drug users in the current and ex-smoker groups (32% and 18%, respectively) than in the never-smoked group (5%). About 25% overall were hepatitis C co-infected, but again this varied widely according to smoking status, reflecting higher rates among injection drug users.

With regard to HIV status, about 60% had suppressed viral load (under 50 copies/ml) and the median CD4 cell count was approximately 450 cells/mm3. The average time on combination antiretroviral therapy was about 1.5 years.

Participants in the different smoking status groups had similar frequencies of traditional cardiovascular risk factors including high blood pressure, abnormal blood lipid levels, and higher body mass index.

The researchers looked at a variety of clinical outcomes including myocardial infarction (heart attack), coronary heart disease, and cardiovascular disease including strokes; they also assessed deaths due to all causes. They calculated incidence and mortality rates for each smoking status group, then compared rates across groups.

Compared with people who never smoked, current smokers had more than three times the risk of myocardial infarction (incident rate ratio [IRR] 3.4) and ex-smokers approached twice the risk (IRR 1.73).

Among the participants who quit smoking during follow-up, the excess risk dropped from 3.7-fold higher during the first non-smoking year, to 3.0-fold after one to two years, and to 2.1-fold after more than three years without smoking.

Similar patterns were seen for coronary heart disease and the broader cardiovascular disease category.

Current smokers had 2.2-fold higher risk of cardiovascular disease relative to non-smokers, and ex-smokers had a 1.4-fold higher risk.

Again, among people who quit during the study, excess risk declined steadily for more than three years (the maximum duration of follow-up).

Looking at all-cause mortality, the pattern was somewhat different. The risk of death was higher among current smokers, but the 1.3-fold risk increase was not as large as those for the clinical events.

Former smokers had the same risk of death as people who had never smoked. But among those who quit during the study, the excess risk of death did not decline in a consistent manner over time; the pattern was also inconsistent when looking only at deaths of people older than 50 years.

The researchers were not able to explain this unexpected finding. However, they did note that a larger proportion of people who never smoked had died of HIV/AIDS-related causes, while current and previous smokers were more likely to die of other causes.

Quitters had an increased risk of non-AIDS cancers, suggesting that damage done while smoking carried over into the smoke-free period.

"The risk of [cardiovascular disease] events in HIV-positive patients decrease with increasing time since stopping smoking," the D:A:D researchers concluded. "Smoking cessation efforts should be a priority in the management of HIV-positive patients."

At a press conference discussing these findings, Dr Petoumenos said that the key take-home message of the study is that the clinical benefits of smoking cessation observed in the general population appear to also apply to HIV-positive people as well.

Further information

You can view the abstract on the official conference website.

You can also view a webcast and slides of this session on the official conference website.

References

Petoumenos K et al. Rates of cardiovascular disease following smoking cessation in patients with HIV infection: results from the D:A:D study. Seventeenth Conference on Retroviruses and Opportunistic Infections, abstract 124, San Francisco, 2010.