1 Introduction
1.1 Background and policy context
Tobacco dependency remains one of the leading causes of preventable illness and premature mortality. In response to this, the NHS Long Term Plan committed to providing NHS-funded tobacco dependence treatment (TTD) services to all patients admitted to acute hospitals in England.
The Hospital-TTD-Mod was developed to support the commissioning, evaluation, and optimisation of these services. Initial development originated from commissioned work by NHS England to review and consolidate previous modelling approaches regarding the return-on-investment of hospital TTD services. The architecture was advanced to evaluate the acute inpatient component of the QUIT programme in South Yorkshire, supported by Yorkshire Cancer Research. Most recently the initial Excel version of the model has been translated into R code in order to accommodate necessary improvements and to efficiently compute estimates for multiple sub-national geographies.
1.2 The need for a new modelling approach
Historically, evaluations of hospital TTD services in England relied on static decision-analytic models. These models were heavily based on the Canadian Ottawa Model for Smoking Cessation (Mullen et al. 2016), applying clinical hazard ratios and absolute risk reductions directly to local hospital data.
A methodological review of previous models revealed methodological issues that risked artificially inflating the estimated cost savings:
Misapplication of risk reduction: Models frequently applied an absolute reduction in readmission risk (e.g., 11.6%) to all patients who took up the intervention, rather than strictly to the subset of patients who actually successfully quit smoking.
No disease specific epidemiology: Models applied a flat hazard ratio uniformly across all future events, failing to account for the gradual, disease-specific decay of risk following cessation.
The Hospital-TTD-Mod addresses these methodological limitations. By transitioning to a deterministic, multi-year Lexis simulation architecture, the model restricts physiological benefits strictly to successful quitters, and applies realistic risk decay curves over time.
1.3 Model objectives and scope
The primary objective of the Hospital-TTD-Mod is to provide a realistic, health-economic evaluation of hospital-based tobacco dependence treatment.
The model is designed to:
Simulate patient flow through the Acute Care hospital inpatient pathway (screening, specialist assessment, and pharmacotherapy).
Project short-term and long-term smoking cessation outcomes.
Use epidemiological potential impact fractions (PIFs) and disease-specific risk decay curves to estimate the reduction in hospital readmissions.
Evaluate cost-effectiveness from two distinct perspectives: short-term acute hospital budget impact (Tier 1) and long-term societal cost-utility (Tier 2).
Quantify the impact of the intervention on health inequalities by stratifying outcomes by age, sex, and socioeconomic deprivation.
1.4 Structure of this technical report
This document provides the full technical specification for the Hospital-TTD-Mod. The report is structured to reflect the sequential execution of the model pipeline:
Chapter 2 outlines the external data sources and literature parameters used to populate the model.
Chapter 3 describes the data processing and preparation pipeline, including the calibration of local smoking prevalence.
Chapter 4 details the clinical pathway model and the methodology for calculating quitting probabilities.
Chapter 5 explains the epidemiological model, the multi-year Lexis loop, and the application of mortality survival constraints.
Chapter 6 defines the health economic evaluation framework and the calculation of incremental cost-effectiveness ratios (ICERs).
Chapter 7 provides an overview of the system diagnostics, methodological reconciliation, and health inequalities reporting.
Chapter 8 serves as a usage guide for analysts operating the codebase.