Association Between Air Quality Index (AQI) Variability and Hospital Admissions for Lung Diseases: A Longitudinal Study
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Background
Severe air pollution in Dhaka, Bangladesh has serious implications for health and well-being, especially respiratory health. The present study examines an association between daily fluctuations in the Air Quality Index (AQI) and hospital admissions for major lung disease among patients at Dhaka Medical College and Hospital (DMCH) in a sample of patients seen from 2020-2024, a time that included a variety of weather environmental conditions and public health scenarios (including the COVID-19 pandemic).
Methods
We conducted a longitudinal ecological time-series study which evaluated the relationship between air quality and respiratory health outcomes. We collected daily data on hospital admissions due to asthma, chronic obstructive pulmonary disease (COPD), acute bronchitis, and pneumonia from the records of Dhaka Medical College Hospital (DMCH), from January 1, 2020 to December 31, 2024. We acquired daily mean Air Quality Index (AQI) values [1], and the concentrations of air pollutants, particulate matter (PM2.5, PM10), nitrogen dioxide (NO2), and sulphur dioxide (SO2), from the Department of Environment (DoE) Bangladesh, and verified this data with publicly available air quality monitoring networks. We also collected meteorological data including daily temperature and humidity. We utilized time-series Poisson regression models incorporating distributed-lag models (DLM) to investigate the short-term relationships and lag-onset effects of AQI and individual pollutants on asthma, COPD, bronchitis, and pneumonia using the disease-specific and all-cause respiratory admissions as the outcomes, adjusting for seasonality, meteorological variables, day of week, public holidays, and significant periods of influenza or COVID-19 outbreaks
Results
Approximately 52,850 hospital admissions for targeted lung diseases were examined over the five-year study period. The annual average air quality index (AQI) in Dhaka was either in the ‘Unhealthy’ or ‘Very Unhealthy’ range and the mean PM2.5 concentrations were much higher than the WHO guidelines [2] for all years. The annual average PM2.5 levels were approximately: 75 µg/m 3 in 2020, 77 µg/m 3 in 2021, 76 µg/m 3 in 2022, 80 µg/m 3 in 2023, and 78 µg/m 3 in 2024. A 10-unit increase in daily overall AQI was associated with a daily increase of 3.8% (95% CI: 3.1-4.5%) of total respiratory hospital admissions. Of the measured pollutants, PM2.5 had the highest association with a 10 µg/m 3 increase linked to a 5.2% (95% CI: 4.3-6.1%) increase in admissions. There was the strongest effect on overall respiratory admissions between lag days 1 to 3. COPD exacerbations and pneumonia admissions were the most sensitive to AQI variabilities. Older adults (> 60 years) and children (< 5 years) were identified as the most vulnerable demographic groups. Winter seasons reported the highest pollution levels over the years of the study, which were linked to the peak respiratory admissions. There were complex interactions with the COVID-19 period where blips in admissions included initially lower levels of non-COVID respiratory admissions during lockdowns and eventually increased levels when restrictions were lifted.
Conclusion
The consistent high levels of air pollution in Dhaka, especially PM2.5, are significantly associated with hospital admissions for several lung diseases. Our findings illuminate some vulnerable populations and highlight an ongoing public health crisis attributable to persistent air quality issues. Regulatory enforcement, appropriate public health intervention, and management of air quality must be amplified to alleviate the burden on the population of Dhaka.
