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Smoking more harmful than HIV for people taking effective treatment, US study suggests
Keith Alcorn, 2016-11-08 06:50:00
Smoking has the potential to shorten the life of a person
taking HIV treatment by an average of six years, and is far more harmful to the
life expectancy of people living with HIV than well-managed HIV infection itself, a US study
reports this month in the Journal of
The study found that stopping smoking improved life expectancy, with the greatest gain in life expectancy seen when smoking was stopped by the age of 40.
Dr Rochelle Walensky of the Massachusetts General Hospital Division of Infectious
Diseases, senior author of the study, said, "It is time to recognise that
smoking is now the primary killer of people with HIV who are receiving
Smoking reduces life expectancy through cardiovascular
disease (stroke and heart attack), cancers and chronic obstructive pulmonary
disease (emphysema). In the United States general population the prevalence of smoking
has declined from 42% in 1965 to 17% in 2014, but a 2015 study estimated that
40% of people living with HIV in the United States still smoke.
To investigate the impact of smoking on life expectancy
among people living with HIV and on treatment in the United States, researchers at Massachusetts
General Hospital developed a model of the impact of smoking and smoking cessation in this population.
The study used data from the North American AIDS Cohort
Collaboration (NA-ACCORD) to create a model of the population living with HIV
in the United States and receiving care. The researchers then modelled the
impact of persistent smoking, stopping smoking or never smoking on the life
expectancy of people living with HIV, assuming that everyone started treatment with
a highly effective antiretroviral regimen on entry to care at the age of 40. The
age of 40 was chosen because NACCORD found that the median age at entry to HIV
care in its participating cohorts was 43 years.
The model assumed that people would enter care with a mean
CD4 cell count of 360 cells/mm3 and then compared the effect of
entering care at the age of 40 or at 50, so as to model the interaction between
later HIV infection and smoking.
Estimates of the impact of smoking on life expectancy were
derived from US general population mortality figures, and also assumed that the
risk of death would begin to diminish for those who gave up smoking depending
on the age at which they stopped. So, for people who gave up at the age of 35,
the risk of death had fallen to the same level as the risk of death for those
who never smoked by the age of 40, but for those who didn’t give up until the
age of 55, the risk of death remained 70% higher than for never-smokers. This
adjustment reflects the accumulated damage caused by smoking.
The study also adjusted for sex – the risk of death was
persistently lower for women who smoked, at all ages – and for higher mortality
in HIV exposure categories other than men who have sex with men.
The model produced from these inputs showed that male smokers
who entered care at the age of 40, and who kept smoking, had an estimated life
expectancy of 65.2 years. Former smokers who quit at the age of 40 would live to the age of 70.9 years
and those who never smoked to the age of 71.9 years. Women who entered care at
the age of 40, and who kept smoking had an estimated life expectancy of 69.9
years. Women who had stopped smoking would live to 72.7 years and those who
never smoked would live to 74.4 years.
This compares with the World Health Organization’s estimate
of an overall life expectancy for the general population in the United States
of 79.3 years (76.9 for men and 81.6 for women). Life expectancy is two to
three years higher in Western Europe, Japan and Australasia.
The model finds that the loss of life expectancy due to
smoking for people living with HIV is probably greater than the loss of life expectancy
due to HIV infection. Indeed, one
study in the United Kingdom has found that people with HIV who have a good
response to treatment may have life expectancy that matches the general
The model found that stopping smoking at 40 resulted in a
gain in life expectancy of 5.7 years for men and 4.6 years for women.
Entering care at 50 years – indicating later infection with
HIV – was associated with longer life expectancy among smokers but also a less
pronounced difference in life expectancy between smokers and former smokers. Male
smokers who entered HIV care could expect to live to 69.9 years, those who quit
to 73.4 years and those who never smoked to 76.5 years. Women who continued to
smoke after entering care at the age of 50 could expect to live to 72.4 years,
those who quit to 75.7 years and those who never smoked to 78.8 years.
The study also found that stopping smoking at the age of 40
was associated with greater gains in life expectancy for both men and women
than starting antiretroviral treatment at a CD4 count above 500 compared to
Based on previous cohort studies, the researchers estimated
that 40% of people living with HIV in the United States are current smokers and
20% ex-smokers. They calculated that if 10% - 25% of current smokers with HIV
aged 30-64 were to stop smoking, between 106,000 and 265,000 extra years of
life would be gained.
The study authors point out that a much lower proportion of
people living with HIV quit smoking compared to the rest of the population, and
that “smoking cessation should be a major priority in HIV carer programs.”
An accompanying editorial commentary by Keri Althoff of
Bloomberg School of Public Health, Johns Hopkins University, Baltimore,
discusses some of the challenges of improving smoking cessation rates in HIV
care, and potential solutions.
A combination of pharmacological treatment and counselling
to assess readiness to quit has proved successful, but cessation rates are
still “disheartening”, she writes. Integrating smoking cessation into a
comorbidities prevention package of care requires a degree of sensitivity:
patients may be overwhelmed by interventions to address mental health issues,
weight and smoking on entry to care, and interventions need to be carefully
Retention in care could be adversely affected if patients
face too many demands at once. “Implementing the intervention among patients
who have achieved stability during ART may be preferable, as patients will have
demonstrated success with an intervention and may be more ready to tackle
another health issue,” she suggests.
Recording of tobacco use in the electronic medical record
should ideally prompt automatic linkage to local resources for smoking
cessation outside the HIV clinic, reducing barriers to accessing these