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. 2024 Jun;27(6):e26315.
doi: 10.1002/jia2.26315.

Tobacco smoking, smoking cessation and life expectancy among people with HIV on antiretroviral therapy in South Africa: a simulation modelling study

Acadia M Thielking  1 , Kieran P Fitzmaurice  1 , Ronel Sewpaul  2 , Stavroula A Chrysanthopoulou  3 , Lotanna Dike  1 , Douglas E Levy  4   5   6 , Nancy A Rigotti  4   5   6   7 , Mark J Siedner  1   4   8   9 , Robin Wood  10   11 , A David Paltiel  12 , Kenneth A Freedberg  1   4   7   8   13 , Emily P Hyle  1   4   8 , Krishna P Reddy  1   4   5   14
Affiliations

Tobacco smoking, smoking cessation and life expectancy among people with HIV on antiretroviral therapy in South Africa: a simulation modelling study

Acadia M Thielking et al. J Int AIDS Soc. 2024 Jun.

Abstract

Introduction: As access to effective antiretroviral therapy (ART) has improved globally, tobacco-related illnesses, including cardiovascular disease, cancer and chronic respiratory conditions, account for a growing proportion of deaths among people with HIV (PWH). We estimated the impact of tobacco smoking and smoking cessation on life expectancy among PWH in South Africa.

Methods: In a microsimulation model, we simulated 18 cohorts of PWH with virologic suppression, each homogenous by sex, initial age (35y/45y/55y) and smoking status (current/former/never). Input parameters were from data sources published between 2008 and 2022. We used South African data to estimate age-stratified mortality hazard ratios: 1.2-2.3 (females)/1.1-1.9 (males) for people with current versus never smoking status; and 1.0-1.3 (females)/1.0-1.5 (males) for people with former versus never smoking status, depending on age at cessation. We assumed smoking status remains unchanged during the simulation; people who formerly smoked quit at model start. Simulated PWH face a monthly probability of disengagement from care and virologic non-suppression. In sensitivity analysis, we varied smoking-associated and HIV-associated mortality risks. Additionally, we estimated the total life-years gained if a proportion of all virologically suppressed PWH stopped smoking.

Results: Forty-five-year-old females/males with HIV with virologic suppression who smoke lose 5.3/3.7 life-years compared to PWH who never smoke. Smoking cessation at age 45y adds 3.4/2.4 life-years. Simulated PWH who continue smoking lose more life-years from smoking than from HIV (females, 5.3 vs. 3.0 life-years; males, 3.7 vs. 2.6 life-years). The impact of smoking and smoking cessation increase as smoking-associated mortality risks increase and HIV-associated mortality risks, including disengagement from care, decrease. Model results are most sensitive to the smoking-associated mortality hazard ratio; varying this parameter results in 1.0-5.1 life-years gained from cessation at age 45y. If 10-25% of virologically suppressed PWH aged 30-59y in South Africa stopped smoking now, 190,000-460,000 life-years would be gained.

Conclusions: Among virologically suppressed PWH in South Africa, tobacco smoking decreases life expectancy more than HIV. Integrating tobacco cessation interventions into HIV care, as endorsed by the World Health Organization, could substantially improve life expectancy.

Keywords: HIV; South Africa; antiretroviral therapy; smoking; smoking cessation; tobacco.

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Conflict of interest statement

KPR reports a grant from the American Lung Association to his institution and royalties from UpToDate, Inc., for authorship of an article about electronic cigarettes. NAR reports a grant to her institution and consulting fees from Achieve Life Sciences, membership in a data and safety monitoring board for Achieve Life Sciences, and royalties from UpToDate, Inc., for authorship of articles about tobacco cessation.

Figures

Figure 1
Figure 1
Life expectancy by smoking status among females and males with HIV on antiretroviral therapy in South Africa. Model‐projected life expectancy among (a) females and (b) males with virologic suppression at model start, stratified by age at model start and smoking status. Individuals can experience virologic failure during the simulation. People with current smoking status continue to smoke until death. People with former smoking status quit at model start and remain abstinent. Life expectancy is expressed as the age at the time of death. Numbers in white quantify the difference in life‐years between people with former or never smoking status compared with people with current smoking status. aWe assume there is no excess mortality risk among people with HIV who quit smoking before age 40y compared to people with HIV who never smoke [15, 35]. Hence, the life expectancy for people with former smoking status and people with never smoking status is the same among those aged 35y at model start.
Figure 2
Figure 2
Survival curves stratified by smoking status among females and males with HIV virologically suppressed on antiretroviral therapy in South Africa. Model‐projected Kaplan−Meier survival curves by smoking status (current, former, never) for 35, 45 and 55‐year‐old females and males with virological suppression at model start. Simulated individuals can experience viraemia during the simulation. People who currently smoke continue to smoke until death. People who formerly smoked quit at model start and remain abstinent. Simulations assume that people who quit prior to age 40y experience no excess mortality from smoking [15, 35]. Vertical dotted lines represent the life expectancy for people of each smoking status.
Figure 3
Figure 3
Sensitivity analysis results when varying key parameters: life‐years gained from smoking cessation among 45‐year‐old females and males with HIV on antiretroviral therapy in South Africa. The bars represent the life‐years gained from smoking cessation (the difference in life expectancy between CS and FS) among females and males aged 45y at model start. Results are reported for sensitivity analysis varying assumptions and parameters associated with smoking (Panel A) and HIV (Panel B). In the base case, represented by the red bar in both panels, smoking cessation occurs at model start (age 45y) and all people are virologically suppressed at model start. Abbreviations: ART, antiretroviral therapy; HR, hazard ratio; PWH, people with HIV; SADHS, South Africa Demographic and Health Survey.
Figure 4
Figure 4
Two‐way sensitivity analysis results: the impact of varying the smoking‐associated mortality hazard ratios and the probability of disengagement from HIV care on life‐years gained from smoking cessation. This figure illustrates the life‐years gained from smoking cessation when varying the mortality hazard ratios for people with current versus never smoking status and the probability of disengagement from HIV care. In this sensitivity analysis, each mortality hazard ratio is applied in a consistent manner to all age groups >40y (i.e. the hazard ratios are not age‐stratified). The “average” hazard ratio in the base case lies between 1.7−2.0 for females and 1.5−1.7 for males, with a 0.7% monthly probability of disengagement from HIV care. †The base case monthly probability of disengagement from HIV care is 0.7%.
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