Clinical benefits of stopping smoking: CVD and CHD risk returns to that of ‘previous smoker’ in HIV-positive people within three years

2 April 2010. Related: Conference reports, Lipodystrophy and metabolic complications, Cancer and HIV, CROI 17 (Retrovirus) 2010.

Simon Collins, HIV i-Base

An analysis from the D:A:D study, presented as an oral session, reported that HIV positive people who stop smoking can expert similar direct health benefits to HIV negative people. 

Kathy Petoumenos from the University of New South Wales, Sydney, looked at rates of cardiovascular disease before and after stopping smoking in over 27,500 HIV-positive patients from Europe, the US and Australia, who had smoking status recorded in the prospective D:A:D cohort study.

The group looked at four endpoints: fatal and non-fatal myocardial infarction (MI), a broader definition of coronary heart disease (CHD), cardiovascular disease (CVD) combining CHD and stroke, and all cause mortality. Event rates were calculated for never smokers (n=8,920), ex-smokers at D:A:D study entry (n=6,265), current smokers (n=11,951), and smokers who stopped during D:A:D follow-up (n=8,197).

Current smokers were more likely to be male (77%), white (70%), infected through IV drug use (32%) and HCV-positive (34%), but CD4, viral load, BP, lipids and ARV-exposure were broadly similar between groups.

Incidence rate ratios (IRR) were determined adjusting for age, sex, cohort, calendar year, antiretroviral treatment, family history of CVD, diabetes (men and women), and time updated lipids and blood pressure assessments. Mortality endpoint also adjusted for HCV, HBV, mode of HIV exposure, ethnicity and incidence of CVD during follow-up.

Up to February 2008, there were 432 (MI), 600 (CHD), 746 (CVD) and 1902 (mortality events) endpoints. Crude event rates were 2.85, 3.96, 4.94, and 12.45 per 1000 person years respectively.

With never-smoked as the reference, increased risks rates were 1.73 and 3.40 for previous- and current-smokers respectively. Rate ratios for patients who had stopped smoking for <1, 1-2, 2-3 and >3 years follow-up since quitting, were 3.73, 3.00, 2.62 and 2.07 respectively, compared to never-smokers. This showed significant reductions within a year of stopping that continued to reduce over subsequent years. A similar pattern was seen for CHD and CVD, and although these were not significant at all timepoints, this is likely to be related to the lower number of events in some groups and the lower number of people who stopped smoking more than two years ago. The protective trend here is clear and important (see Table 1).

Although current smokers were at 28% higher risk of mortality, with no difference between never- and former-smokers, no clear reductions were seen during follow-up since stopping, with all confidence intervals crossing 1.0, even in a sub-group at higher risk of CVD-related mortality (in patients older than 50 years).

Table 1: Incidence rate ratios by baseline smoking status and time since quitting

* Non significant (CI crossed 1.0)

An explanation for the higher rates seen in the most recent (< 1 year) quitters was explained by the likelihood that a medical incident could have been the prompt needed to stop smoking. This group would therefore be at higher risk compared to current smokers (who would have been symptomatic). This was supported by the cause of mortality being more likely to be HIV/AIDS in the never smoked group with higher rates of non-AIDS malignancies seen in the previous and stopped groups.

The study has limitations in the amount and type of data that were collected on smoking (e.g. no start/stop dates or pack-year data). However, the significant reductions on CHD with each year after stopping smoking should support cessation programme for HIV-positive people, a greater percentage of whom smoke than the general population.

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This is the first time that the clinical benefits of stopping smoking has been reported in HIV-positive people and these findings should not be taken for granted. 

Each year, HIV-positive people are advised on the importance of modification of lifestyle for ‘healthy options’ related to the complicated etiology of cardiovascular health and any study that can show tangible benefits is important.

This is particularly important given the higher rates of lung cancers reported in other studies. Keith Sigel and colleagues reported that HIV is an independent risk factor for lung cancer after adjusting for smoking (IRR 1.80; 95%CI 1.28 2.15). [2]

Edgar Simard from the US National Cancer Institute, reported a 3-fold observed incidence of lung cancer in HIV-positive patients within 3-5 years of an AIDS diagnosis compared to the general population (and increasing cumulative incidence). [3]

Meredith Shiels and colleagues reported that lung cancer was one of the cancers that was being diagnosed at an earlier age in HIV-positive compared to HIV-negative people, and that this 3-4 year difference was statistically significant after adjustment for multiple comparisons (p<0.001). [4]

References

Unless stated otherwise, all references are to the Programme and Abstracts of the 17th Conference on Retroviruses and Opportunistic Infections. 16-10 February 2010, San Francisco. All oral abstracts are available as webcasts.
http://www.retroconference.org

1. Petoumenos K et al. Rates of cardiovascular disease following smoking cessation in patients with HIV infection: results from the D:A:D study. 17th CROI, 2010. Oral abstract 124.
   http://www.retroconference.org/2010/Abstracts/38289.htm
2. Sigel K et al. HIV infection is an independent risk factor for lung cancer. 17th CROI, 2010. Oral Abstract 30.
   http://www.retroconference.org/2010/Abstracts/38365.htm
3. Simard E et al. Cancer incidence and cancer-attributable mortality among persons with AIDS in the US. 17th CROI, 2010. Oral abstract 27.
   http://www.retroconference.org/2010/Abstracts/38173.htm
4. Shiels M et al. Do people with AIDS develop cancer at younger ages than the general population? 17th CROI, 2010. Poster 757.
   http://www.retroconference.org/2010/Abstracts/37914.htm