Exposure to air pollution and risk of hospitalization for cardiovascular diseases amongst Vietnamese adults: Case-crossover study

Background: Associations between hospital admissions and ambient air pollutants in the Vietnamese population have been reported in previous studies. However, most studies were conducted in Hanoi or Hochiminh city. We used hospital records of seven hospitals in Northern Vietnam to investigate short-term associations between ambient air pollutants and hospital admissions due to cardiovascular conditions. Methods: We used 135'101 hospital records of residents (age >= 15) living in three provinces (Hanoi, Quang Ninh, and Phu Tho) and daily ambient air pollutant concentrations to estimate percentage changes and 95% confidence intervals for hospital admissions due to seven cardiovascular conditions per interquartile range (IQR) increases in daily ambient air pollutants. We used a time-stratified case-crossover analysis adjusting for meteorological factors, indicators of holidays and influenza epidemics. We also investigated modification of effects by age groups (<65 and >= 65), seasons (cold and hot) and hospital levels (national and province level). Results: Particulate matter concentrations were positively associated with daily hospital admissions due to most cardiovascular conditions. For example, an increment in the two-day average (lag1-2) level of PM2.5 by one IQR (34.4 mg/m(3)) was associated with a 6.3% (95%CI: 3.0%-9.8%) increase in the daily count of admissions for ischemic heart disease in Hanoi and with 23.2% (95%CI: 11.1%-36.5%) for cardiac failure in Quang Ninh. Moreover, hospitalisations for stroke in Hanoi and cardiac failure in Phu Tho showed strong positive associations with SO2. The findings also show that estimates varied by age groups, seasons and hospital levels. Conclusion: Ambient air pollutants were associated with daily cardiovascular admissions in Northern Vietnam. The findings underline the important role of ambient air pollutants as a trigger of cardiovascular conditions. (C) 2019 Elsevier B.V. All rights reserved.