Air Health Effects Science Division, Health Canada, Ottawa, Canada; Department of Environmental and Occupational Health, University of Montreal, Montreal, Canada.
McGill University Health Center, Division of Clinical Epidemiology, Montreal, Canada.
Environ Res. 2015 Feb;137:323-8. doi: 10.1016/j.envres.2015.01.006. Epub 2015 Jan 17.
We examined the impact of data source and exposure measurement error for ambient NO2 on risk estimates derived from a case-crossover study of emergency room visits for asthma in Windsor, Canada between 2002 and 2009.
Paired personal and fixed-site NO2 data were available from an independent population (47 children and 48 adults) in Windsor between 2005 and 2006. We used linear regression to estimate the relationship and measurement error variance induced between fixed site and personal measurements of NO2, and through a series of simulations, evaluated the potential for a Bayesian model to adjust for this change in scale and measurement error. Finally, we re-analyzed data from the previous case-crossover study adjusting for the estimated change in slope and measurement error.
Correlations between paired NO2 measurements were weak (R(2)≤0.08) and slopes were far from unity (0.0029≤β≤0.30). Adjusting the previous case-crossover analysis suggested a much stronger association between personal NO2 (per 1ppb) (Odds Ratio (OR)=1.276, 95% Credible Interval (CrI): 1.034, 1.569) and emergency room visits for asthma among children relative to the fixed-site estimate (OR=1.024, 95% CrI 1.004-1.045).
Our findings suggest that risk estimates based on fixed-site NO2 concentrations may differ substantially from estimates based on personal exposures if the change in scale and/or measurement error is large. In practice, one must always keep the scale being used in mind when interpreting risk estimates and not assume that coefficients for ambient concentrations reflect risks at the personal level.
我们研究了 2002 年至 2009 年间加拿大温莎市因哮喘急诊就诊的病例交叉研究中，环境二氧化氮（NO2）的数据源和暴露测量误差对风险估计的影响。
2005 年至 2006 年，温莎市一个独立人群（47 名儿童和 48 名成年人）提供了配对的个人和固定站点 NO2 数据。我们使用线性回归来估计固定站点和个人 NO2 测量之间的关系和测量误差方差，并通过一系列模拟评估贝叶斯模型调整这种规模和测量误差变化的潜力。最后，我们重新分析了之前病例交叉研究的数据，调整了估计的斜率和测量误差变化。
配对 NO2 测量之间的相关性较弱（R2≤0.08），斜率远非 1（0.0029≤β≤0.30）。调整之前的病例交叉分析表明，个人 NO2（每 1ppb）（比值比（OR）=1.276，95%可信区间（CrI）：1.034，1.569）与儿童哮喘急诊就诊之间的关联比固定站点估计要强得多（OR=1.024，95% CrI 1.004-1.045）。
如果规模和/或测量误差变化较大，基于固定站点 NO2 浓度的风险估计可能与基于个人暴露的估计有很大差异。在实践中，在解释风险估计时，人们必须始终牢记使用的规模，而不能假设环境浓度的系数反映个人水平的风险。
