Abstract
BackgroundAir pollution in Beijing, especially PM2.5, has received increasing attention in the past years. Although exposure to PM2.5 has been linked to many health issues, few studies have quantified the impact of PM2.5 on the risk of influenza-like illness (ILI). The aim of our study is to investigate the association between daily PM2.5 and ILI risk in Beijing, by means of a generalized additive model.MethodsDaily PM2.5, meteorological factors, and influenza-like illness (ILI) counts during January 1, 2008 to December 31, 2014 were retrieved. An inverse Gaussian generalized additive model with log link function was used to flexibly model the nonlinear relationship between the PM2.5 (single- and multiday lagged exposure) and ILI risk, adjusted for the weather conditions, seasonal and year trends. We also assessed if the effect of PM2.5 differs during flu season versus non-flu season by including the interaction term between PM2.5 and flu season in the model. Furthermore, a stratified analysis by age groups was conducted to investigate how the effect of PM2.5 differs across age groups.ResultsOur findings suggested a strong positive relationships between PM2.5 and ILI risk at the flu season (October-April) (p-value < 0.001), after adjusting for the effects of ambient daily temperature and humidity, month and year; whereas no significant association was identified at the non-flu season (May-September) (p-value = 0.174). A short term delayed effect of PM2.5 was also identified with 2-day moving average (current day to the previous day) of PM2.5 yielding the best predictive power. Furthermore, PM2.5 was strongly associated with ILI risk across all age groups (p-value < 0.001) at the flu season, but the effect was the most pronounced among adults (age 25–59), followed by young adults (age 15–24), school children (age 5–14) and the elderly (age 60+) and the effect of PM2.5 was the least pronounced for children under 5 years of age (age < 5).ConclusionsAmbient PM2.5 concentrations were significantly associated with ILI risk in Beijing at the flu season and the effect of PM2.5 differed across age groups, in Beijing, China.
Highlights
Air pollution in Beijing, especially PM2.5, has received increasing attention in the past years
Our results indicated that at the flu season, PM2.5 was strongly associated with influenza-like illness (ILI) risk across all age groups (p-value < 0.001), but PM2.5 had the greatest effect sizes for adults, followed by young adults, and elderly and school age children and the PM2.5 has the least pronounced effect for the children under 5 years of age
Such associations are not confounded by long-term time trends, or by weather conditions, all of which were properly controlled in the generalized additive model
Summary
Air pollution in Beijing, especially PM2.5, has received increasing attention in the past years. Exposure to PM2.5 has been linked to many health issues, few studies have quantified the impact of PM2.5 on the risk of influenza-like illness (ILI). The aim of our study is to investigate the association between daily PM2.5 and ILI risk in Beijing, by means of a generalized additive model. Air pollution has been well documented as a major public health issue for many areas of the world, as a growing body of epidemiological and clinical evidence has shown that pollutants increase the risks of numerous diseases [1,2,3,4,5,6,7]. PM10 consists of two size fractions, fine and coarse, which have both different physiologic and different source characteristics. Particles resulting from combustion processes are generally less than 2.5 μm, which are defined as fine particles (PM2.5)
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