Thursday, January 10, 2013

Mortality attributable to smoking among HIV-1-infected individuals

Reposted at

Anyone else read the recent publication "Mortality attributable to smoking among HIV-1-infected individuals" in Clinical Infectious Disease? 

A summary from  is included at the bottom for those without academic journal access.

The main figure: Number of Life-Years Lost:

HIV among never smokers: 5.1 

(never smoking HIV patients vs never smoking controls)

Smoking among controls: 3.6 

(comparing smoking HIV-neg to never smoking HIV-neg) 

Smoking among HIV patients: 12.3

(comparing  smoking HIV+ to non-smoking HIV+)

Though this number is pretty shocking, I find some of the methodology suspect (though I'm no biostatistician - correct me if I'm wrong).
I don't exactly know how the number of life years lost due to smoking could be so different for HIV+ and HIV- groups (12.3 YLLs vs 3.6 YLLs) without an interaction between smoking and HIV (or, alternatively, a very important confounding variable). But they write: "One might speculate that smoking could have a synergistic rather than additive effect on inflammation in HIV-infected individuals, but we found no interaction between HIV and smoking in the associated risk of death."

Also, look at table 2 -  there's such drastic differences in AIDS related mortality for smokers and nonsmokers (considerably more than the disparities in cardiovascular disease), and previous smokers are similar to current smokers rather than non-smokers. To me, this suggests that there are SES or demographic differences between smokers (past or present) and non-smokers that this study is not controlling for that impact access to and retention in care, health behaviors more broadly, etc.

Just wanted to through my 2 cents out there. Interesting work, and I'm glad its being read and forwarded.

 - Sam Bakkila

Michael Carter
Published: 31 December 2012

Much of the increased mortality seen in patients with HIV can be attributed to smoking, Danish investigators report in the online edition of Clinical Infectious Diseases. “The loss of life-years associated with smoking was larger than that associated with HIV,” write the investigators. The authors believe their findings have important implications for HIV care, showing the importance of smoking cessation counselling and support.

Thanks to antiretroviral therapy, the prognosis of many HIV-positive patients is now excellent. Rates of HIV-related illnesses and deaths have fallen dramatically since the mid 1990s, meaning that lifestyle-related factors are now a major cause of morbidity and mortality in HIV-infected individuals.

A number of studies have shown that HIV-positive individuals are more likely to smoke than their HIV-negative peers. Illnesses that are potentially related to smoking, such as cardiovascular disease and cancers, are being seen with increased frequency in HIV-positive patients. The role of smoking and other potentially modifiable risk factors is currently unclear.

Investigators from Denmark therefore designed a study to evaluate the effect of smoking on mortality among patients with HIV. They also compared the risk of death and loss of life-years associated with smoking with the risk associated with HIV-related factors.

The study population involved 2921 adults who received HIV care between 1995 and 2010. Injecting drug users were excluded from participation. The HIV-infected patients were matched with 10,642 controls.

Both the patients and the controls were followed for a median of four years.

Among HIV-positive patients, 47% were current smokers, 18% were former smokers and 35% had never smoked. The corresponding rates for the controls were 21%, 33% and 47%.

The excess mortality rate for HIV-positive current smokers (compared to HIV-positive patients who had never smoked) was 18 per 1000 patient years. The corresponding rate for the HIV-negative controls was 5 per 1000 patient years.

The risk of non-HIV-related death was five-fold higher for current smokers compared to HIV-infected patients who had never smoked. HIV-positive patients who were current smokers also had a four-fold increase in their risk of all-cause mortality.

The risk of death due to cardiovascular disease was approximately two times higher for HIV-positive current smokers compared to HIV-positive non-smokers. Current smokers were also three times more likely to die of cancer.

Smoking had a significant impact on the life expectancy of HIV-positive patients.

The authors calculated that 35-year-old non-smokers had a life expectancy of 78 years. This compared to a life expectancy of 69 years for former smokers, and a life expectancy of just 63 years for current smokers.

“Our finding of lower mortality among previous compared to current smokers emphasizes the importance of counseling HIV patients onsmoking cessation,” comment the researchers.

They calculated that the HIV-positive patients lost five years of life expectancy due to their HIV infection and that twelve life years were lost because of smoking.

“The loss of life-years associated with smoking was larger than that associated with HIV,” write the investigators. “HIV-infected smokerswith long-term engagement in care lose more life-years to smoking than HIV.”


Helleberg M et al. Mortality attributable to smoking among HIV-1-infected individuals: a nationwide population-based cohort study. Clin Infect Dis, online edition. DOI: 10.1093/cid/cis933, 2012.


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