Ambient temperature variability and newly diagnosed tuberculosis: Evidence from a time-stratified case-crossover study.

Background: Environmental factors, particularly temperature-related exposures, are increasingly recognized as important determinants of tuberculosis (TB) disease progression and symptom manifestation. However, the evidence regarding the associations of heat exposure, cold exposure, and diurnal temperature range (DTR) with newly diagnosed TB remains limited and inconsistent. Methods: Data from Anhui Province between 1 January 2015 and 31 December 2024 were analyzed using a two-stage analytical framework based on a time-stratified case-crossover study design. City-specific associations between temperature and TB were pooled using a random-effects meta-analysis. Effect estimates were presented as relative risks (RRs) with corresponding confidence intervals (CIs). Results: A total of 243,577 newly diagnosed TB cases were reported during the study period. Compared with the median daily mean temperature, extreme heat exposure (95th percentile of daily mean temperature) was positively associated with newly diagnosed TB (RR = 1.218, 95% CI = 1.171, 1.267). In contrast, extreme cold exposure (fifth percentile of daily mean temperature) was negatively associated with newly diagnosed TB (RR = 0.837, 95% CI = 0.784, 0.893). Additionally, a greater DTR (95th percentile) was positively associated with newly diagnosed TB compared with the median DTR (RR = 1.320, 95% CI = 1.153, 1.512). These associations remained robust across multiple sensitivity analyses. Conclusion: Environmental temperature conditions are significantly associated with TB diagnosis. These findings suggest that temperature variability may influence the timing of TB diagnosis and highlight the importance of incorporating meteorological information into climate-sensitive TB surveillance and public health preparedness.