# Epidemiological analysis and risk factors of recurrent pulmonary tuberculosis in Western Zhejiang Province, China (2007–2024)

## TL;DR

This study examines the recurrence of tuberculosis in western Zhejiang Province, identifying risk factors like age, gender, and occupation to improve prevention and treatment strategies.

## Contribution

The study identifies key risk factors for tuberculosis recurrence and adverse retreatment outcomes in a specific Chinese region.

## Key findings

- Nearly half of tuberculosis recurrences occurred within 2 years after treatment completion.
- Advanced age, male sex, and farming occupation were identified as independent risk factors for recurrence.
- Older patients (≥65 years) faced a higher risk of both recurrence and adverse retreatment outcomes.

## Abstract

Recurrent pulmonary tuberculosis (PTB) after successful treatment is a significant challenge for current TB control efforts. This study investigated the epidemiological characteristics of recurrent PTB in western Zhejiang Province, aiming to identify risk factors for recurrence and predictors of retreatment outcomes, thereby providing a scientific basis for targeted prevention and management.

This retrospective cohort study utilized surveillance data from the Tuberculosis Information Management System in Quzhou, Zhejiang, from January 1, 2007, to December 31, 2024. Recurrence-free intervals were analyzed to identify temporal patterns, and multivariable Cox proportional hazards regression models were employed to determine independent risk factors for recurrence and adverse retreatment outcomes.

Among 28,458 patients, 897 (3.15%) experienced recurrence. These cases were predominantly male (79.2%), older (mean age, 61.6 years), and farmers (80.3%). Recurrence-free intervals significantly shortened with subsequent episodes, dropping from a median of 804 days (95% CI, 740–900) for the first recurrence to 495 days (95% CI, 394–737) for the second (p < 0.001). Nearly half (48.9%) of all recurrences occurred within the first 2 years after treatment. Independent predictors of recurrence included advanced age (Adjusted HR, 1.77 for ≥65 years [95% CI, 1.46–2.16]), male sex (AHR, 1.42 [95% CI, 1.21–1.67]), and farming occupation (AHR, 1.22 [95% CI, 1.02–1.46]). For retreatment outcomes, age ≥65 years was the independent risk factor for adverse events (AHR, 1.91 [95% CI, 1.07–3.40]).

Nearly half of the recurrences occurred within 2 years after treatment completion, and recurrence-free intervals progressively shortened with repeated episodes. The older population (≥65 years) faced a dual burden, identified as the primary risk group for both recurrence and adverse retreatment outcomes. For the risk factors of recurrence and the success of treatment, it is necessary to further refine and explore the influencing factors.