not-yet-known not-yet-known not-yet-known unknown Background Severe air pollution in Dhaka,Bangladesh poses major risks to respiratory health. This study investigates the association between daily AQI fluctuations and hospital admissions for major lung diseases at DMCH from 2020–2024, spanning diverse weather patterns and public health events, including the COVID-19 pandemic. Methods We conducted a longitudinal ecological time-series study from January 1, 2020 to December 31, 2024, assessing the link between air quality and respiratory admissions at Dhaka Medical College Hospital. Daily data on asthma, COPD, bronchitis, and pneumonia admissions were analyzed alongside AQI and pollutant levels (PM2.5, PM10, NO2, SO2) from DoE and public networks. Meteorological data (temperature, humidity) were included. Time-series Poisson regression with distributed-lag models examined short-term and lagged effects, adjusting for seasonality, weather, weekdays, holidays, and flu/COVID-19 outbreaks. Results Over five years, 52,850 lung disease admissions were analyzed. Dhaka’s annual AQI remained ‘Unhealthy’ to ‘Very Unhealthy,’ with PM2.5 levels far exceeding WHO guidelines—ranging from 75–80 µg/m 3 (2020–2024). A 10-unit AQI rise correlated with a 3.8% daily increase in respiratory admissions; a 10 µg/m 3 PM2.5 rise led to a 5.2% increase. Effects peaked at lag days 1–3. COPD and pneumonia were most sensitive, with older adults and children most vulnerable. Winter had the worst pollution and highest admissions. COVID-19 lockdowns briefly reduced non-COVID admissions, which surged post-restrictions. Conclusion Consistently high PM2.5 levels in Dhaka are significantly linked to increased hospital admissions for lung diseases. Our findings reveal vulnerable populations and underscore a public health crisis. Stronger regulatory enforcement and targeted interventions are essential to reduce Dhaka’s air quality burden.