# Long-term mortality and cause of death in people with tuberculosis compared with matched controls with influenza or non-typhoid salmonellosis in Australia: a retrospective cohort study

## TL;DR

This study compares long-term mortality and causes of death in tuberculosis patients with those of influenza and non-typhoid salmonellosis patients in Australia.

## Contribution

It provides new insights into the long-term mortality risks and causes of death specific to tuberculosis survivors compared to other infection groups.

## Key findings

- TB patients had a higher risk of respiratory-related deaths compared to influenza patients.
- Most TB-related deaths occurred within 10 years of diagnosis.
- TB survivors had an 18.7 times higher mortality rate from infectious causes than the general population.

## Abstract

Tuberculosis (TB) patients are thought to experience excess long-term morbidity and mortality. However, the long-term mortality of people with TB has not been compared with other common infections to assess their overall and disease-specific causes of death.

All people diagnosed with TB between 2000 and 2015 in New South Wales, Australia, were matched by age, sex and year of infection to notified cases of influenza or non-typhoid salmonellosis. Patients were linked to the Australian mortality register to assess date and cause of death, up until the end of 2022. The comparative mortality ratio (CMR) for each cohort was calculated and Kaplan-Meier survival curves constructed. The standardised mortality rate (SMR) was estimated using national mortality data.

The CMR of 7386 people with past TB was marginally increased (1.16 with 95% CI 1.10 to 1.22) compared with non-typhoid salmonellosis but reduced compared with influenza (0.88 with 95% CI 0.84 to 0.93). Most deaths occurred within 10 years of the notified infection. For TB patients, 1162 of 1331 people (87.3%) died in the 10 years after TB diagnosis. Risk factors for long-term mortality among TB patients included age over 40 years, male sex, sputum smear-positive and intracranial disease. Respiratory causes of death, including chronic obstructive pulmonary disease, lung cancer and pneumonia, were increased for TB patients, while influenza patients suffered more cardiovascular deaths. The SMR for TB patients (compared with the Australian general population) was increased by 18.7 times for infectious causes of death, 2.8 times for respiratory causes and 1.4 times for cancer-related mortality.

Despite successful treatment, people with TB often experience post-TB sequelae and increased long-term mortality, with increased risk of respiratory causes of death. This highlights the need for appropriate post-TB respiratory follow-up, particularly in the first 10 years after TB diagnosis.