People who are infected with human immunodeficiency virus and who smoke are far more likely to die from lung cancer than HIV, researchers said Monday.
"Having HIV and using tobacco may together accelerate the development of lung cancer," warned the report in the Journal of the American Medical Association (JAMA) Internal Medicine.
Smoking reduces life expectancy among people living with HIV -- and undergoing antiretroviral therapy to keep their disease at bay -- more than HIV itself, it added.
The findings are of particular concern because smoking is so common among people with HIV.
The prevalence of smokers among the population of people with HIV is 40 percent, about twice the rest of the US population.
"Smoking and HIV are a particularly bad combination when it comes to lung cancer," said lead author Krishna Reddy, a doctor at the Massachusetts General Hospital in Boston.
"Smoking rates are extraordinarily high among people with HIV, and both smoking and HIV increase the risk of lung cancer."
Almost 25 percent of people who adhere well to anti-HIV medications but continue to smoke will die from lung cancer, said the findings.
People with HIV who take antiviral drugs and also smoke are from six to 13 times more likely to die from lung cancer than from HIV/AIDS, it added.
But there is hope for those who manage to quit.
Among smokers who quit at age 40, only about six percent will die of lung cancer, according to the study, which is based on projections using a computer model.
"Quitting smoking is one of the most important things that people with HIV can do to improve their health and live longer," said co-author Travis Baggett, also of Massachusetts General Hospital.
Nearly 60,000 of the 644,2000 people aged 20-64 living with HIV and receiving care are expected to die from lung cancer by age 80 if smoking habits do not change.