Bayesian hierarchical distributed lag models for summer ozone exposure and cardio‐respiratory mortality

Abstract

In this paper we develop Bayesian hierarchical distributed lag models for estimating associations between daily variations in summer ozone levels and daily variations in cardiovascular and respiratory (CVDRESP) mortality counts for 19 large U.S. cities included in the National Morbidity Mortality Air Pollution Study (NMMAPS) for the period 1987 -1994.At the first stage, we define a semi-parametric distributed lag Poisson regression model to estimate city-specific relative rates of CVDRESP associated with short-term exposure to summer ozone. At the second stage, we specify a class of distributions for the true cityspecific relative rates to estimate an overall effect by taking into account the variability within and across cities. We perform the calculations with respect to several random effects distributions (normal, t-student, and mixture of normal), thus relaxing the common assumption of a two-stage normal-normal hierarchical model. We assess the sensitivity of the results to: 1) lag structure for ozone exposure; 2) degree of adjustment for long-term trends; 3) inclusion of other pollutants in the model; 4) heat waves; 5) random effects distributions; and 6) prior hyperparameters.On average across cities, we found that a 10ppb increase in summer ozone level for every day in the previous week is associated with 1.25 percent increase in CVDRESP mortality (95% posterior regions: 0.47, 2.03). The relative rate estimates are also positive and statistically significant at lags 0, 1, and 2. We found that associations between summer ozone and CVDRESP mortality are sensitive to the confounding adjustment for P M 10 , but are robust to: 1) the adjustment for long-term trends, other gaseous pollutants (N O 2 , SO 2 , and CO); 2) the distributional assumptions at the second stage of the hierarchical model; and 3) the prior distributions on all unknown parameters.Bayesian hierarchical distributed lag models and their application to the NMMAPS data allow us estimation of an acute health effect associated with exposure to ambient air pollution in the last few days on average across several locations. The application of these methods and the systematic assessment of the sensitivity of findings to model assumptions provide important epidemiological evidence for future air quality regulations.

Reassessing the relationship between ozone and short-term mortality in U.S. urban communities

“…Other authors who have considered the confounding effect of PM 10 as a co-pollutant include Huang et al (2005), who analyzed a subset of the NMMAPS database; when both ozone and PM 10 were included in the model at lag 2, there was a decrement in the ozone-mortality effect similar to that reported here, but at other lags, the effect was smaller or non-existent. Schwartz (2005) also looked at PM 10 confounding in his case-crossover analysis, concluding there was no effect.…”

“…They have been extensively used in the analysis of ozone and mortality -apart from the papers already cited, a smaller multicity study was included in Ito et al (2005), an earlier version of the NMMAPS analysis in Huang et al (2005), and a similar European study in Gryparis et al (2004). They were also used in a widely cited study about PM 2.5 and hospital admissions ).…”

Health Benefits From Large Scale Ozone Reduction In The United States

“…The selection criteria included an array of statistical designs and broad geographic coverage. We chose time-series studies (Bell et al 2004;Huang et al 2005), meta-analyses Ito et al 2005;Levy et al 2005), a case-crossover study (Schwartz 2005), and a cohort study of long-term effects (Jerrett et al 2009). Morbidity studies were primarily time-series analyses although they included fewer cities and years than mortality studies.…”

“…Tropospheric ozone has been associated with adverse health effects, including decreased pulmonary function, asthma exacerbations, increased hospital and emergency department (ED) visits, and increased mortality (Choi et al 2011;Dockery and Pope 1994;Levy et al 2001;Mudway and Kelly 2000). Evidence of negative health effects has been demonstrated by toxicological studies (Larsen et al 2010), clinical trials (Gong et al 1986), longitudinal epidemiological studies (Bell et al 2004;Gryparis et al 2004;Huang et al 2005;Ito et al 2005;Levy et al 2005;Schwartz 2005), and cohort epidemiological studies (Jerrett et al 2009). Adolescents and individuals with existing chronic lung and cardiovascular disease have increased susceptibility to the adverse health effects of ozone (Burnett et al 2001).…”

Bayesian hierarchical modeling of cardiac response to particulate matter exposure

“…Other models relating outdoor PM 2.5 concentrations to meteorological variables are possible (Holloman et al, 2004;Huang et al, 2005) and may more accurately reflect the spatial and temporal variation of PM 2.5 . Equation (2) accounts for an effect due to personal total PM 2.5 at a lag of 1 day.…”