How do climate conditions and urbanisation impact nontuberculous mycobacterial infections? An Italian nationwide case–control study

Introduction: Nontuberculous mycobacteria (NTM) are opportunistic pathogens primarily found in soil and water. Previous studies have linked higher population density and tropical/subtropical climates with increased NTM pulmonary disease (NTM-PD). However, the effects of meteorological parameters and population density on NTM incidence in European countries remain unclear. This study aimed to assess whether climate conditions (temperature, humidity, wind speed, precipitation) and urbanisation influence the occurrence of NTM-PD. Methods: We conducted a case-control study evaluating meteorological conditions (in the 12 months before the first NTM isolate) and urbanisation in the municipalities of residence of 1061 adults with NTM-PD enrolled in an Italian multicentre observational study (2017-2023), compared with a random sample of 10 000 adults from the Italian population. Results: The mean age of patients was 63.1 years, and 67.2% were female. Less densely populated areas were at lower risk for NTM-PD, even after adjusting for age, sex and meteorological parameters in a multivariable mixed-effects logistic regression model (OR 0.66 (95% CI: 0.56-0.78) and 0.68 (95% CI: 0.52-0.89) for semi-urban and rural areas, respectively, versus urban areas). Hotter climates were found to be at higher risk for NTM infection (OR 1.21 (95% CI: 1.10-1.33) for each °C increase in mean annual temperature). More ventilated climates with higher precipitation were at lower risk for NTM infection (OR 0.90 (95% CI: 0.86-0.95) for each km·h-1 increase in mean annual wind speed; OR 0.99 (95% CI: 0.99-0.99) for each 10 mm increase in mean annual precipitation). Conclusions: Climate change, particularly global warming and urbanisation, may increase NTM infections in regions with Mediterranean and continental climates. ( METEO-NTM study group)