People living with HIV underestimate the harm of smoking

People with HIV in Denmark who smoke greatly underestimate the impact of smoking on life expectancy, a study of perceptions of life expectancy published this month in the Journal of Acquired Immune Deficiency Syndromes shows.

Current smokers living with HIV, asked to estimate their life expectancy, anticipated their life expectancy to be 3.65 years lower than people with HIV who had never smoked. However, epidemiological research carried out in Denmark indicates that smoking reduces life expectancy by 12 years in people living with HIV.

In comparison, the overall estimation of life expectancy by people living with HIV was accurate. Danish research estimates that HIV infection will reduce life expectancy by five years compared to the general population. People living with HIV perceived their life expectancy to be almost four-and-a-half years shorter (4.26 years) than people in the general population asked to estimate their life expectancy.


multivariate analysis

An extension of multivariable analysis that is used to model two or more outcomes at the same time.


Studies aim to give information that will be applicable to a large group of people (e.g. adults with diagnosed HIV in the UK). Because it is impractical to conduct a study with such a large group, only a sub-group (a sample) takes part in a study. This isn’t a problem as long as the characteristics of the sample are similar to those of the wider group (e.g. in terms of age, gender, CD4 count and years since diagnosis).


The study of the causes of a disease, its distribution within a population, and measures for control and prevention. Epidemiology focuses on groups rather than individuals.


In a case-control study, a process to make the cases and the controls comparable with respect to extraneous factors. For example, each case is matched individually with a control subject on variables such as age, sex and HIV status. 


Short for people living with HIV.

The study was carried out by researchers at the University of Copenhagen who have previously investigated changes in life expectancy in people living with HIV resulting from successful antiretroviral treatment. Using Denmark’s national cohort of people receiving HIV care, other researchers have looked at the impact of smoking on life expectancy in people living with HIV.

In this study, the University of Copenhagen researchers asked a cohort of 937 people living with HIV and 6147 age-matched controls from the general population what age they expected to live to, and analysed responses based on demographic and behavioural data gathered as part of larger cohort studies.

The median age of participants was 51 years for people living with HIV and 53 years for the general population. The cohort was 88% male. Thirty per cent of people living with HIV were current smokers compared to 14% of the general population sample, and 35% of people living with HIV were former smokers compared to 38% of the general population.

People living with HIV expected to live to the age of 80.5 on average, while people in the general population expected to live to the age of 85.2 years (p < 0.0001).

This differential is remarkably close to the difference in life expectancy estimated in one national cohort study carried out in Denmark, which projected a reduction of 5.1 years in life expectancy compared to the general population for people with HIV taking effective antiretroviral therapy. However, another study which looked at people living with HIV aged 50 and over, found that life expectancy for this group was almost nine years shorter than for the general population.

When asked about the effects of smoking, people living with HIV who smoked estimated that smoking would reduce life expectancy by 3.65 years and general population respondents estimated that it would reduce life expectancy by 4.36 years. Smokers with a longer history of smoking were likely to estimate that smoking had a greater negative impact on life expectancy, so that for every ten years of smoking 20 cigarettes a day, they cut their estimate of life expectancy by 0.69 years.

Factors related to HIV disease such as current CD4 count, viral load, previous AIDS diagnosis or hepatitis C did not affect perceptions of life expectancy among people living with HIV.

Multivariate analysis found that male sex and higher alcohol consumption were each independently associated with modestly lower self-perceived life expectancy. No education after high school was associated with a 1.76-year reduction in estimated life expectancy. HIV was associated with a 4.26-year reduction in estimated life expectancy.

The investigators speculate that the focus on HIV infection, both by healthcare providers and by people living with HIV, has shifted attention away from the harmful effects of smoking.

“Disseminating knowledge about the harmful effects of smoking is a perquisite for an individual to make behavioural changes, and this study emphasizes the need for clinicians to communicate this knowledge to PLWH [people living with HIV],” the study authors conclude.


Ronit A et al. HIV status is a greater determinant of low self-perceived life expectancy than cigarette smoking in a well-resourced setting. J Acquir Immune Defic Syndr, 79: 81-84, 2018.