Department of Environmental Health, Harvard School of Public Health, Boston, MA 02215, USA.
Am J Respir Crit Care Med. 2011 Oct 1;184(7):836-41. doi: 10.1164/rccm.201102-0227OC.
Time series studies have reported associations between ozone and daily deaths. Only one cohort study has reported the effect of long-term exposures on deaths, and little is known about effects of chronic ozone exposure on survival in susceptible populations.
We investigated whether ozone was associated with survival in four cohorts of persons with specific diseases in 105 United States cities, treating ozone as a time varying exposure.
We used Medicare data (1985–2006), and constructed cohorts of persons hospitalized with chronic conditions that might predispose to ozone effects: chronic obstructive pulmonary disease, diabetes, congestive heart failure, and myocardial infarction. Yearly warm-season average ozone was merged to the individual follow-up in each city. We applied Cox proportional hazard model for each cohort within each city, adjusting for individual risk factors, temperature, and city-specific long-term trends.
We found significant associations with a hazard ratio for mortality of 1.06 (95% confidence interval [CI], 1.03–1.08) per 5-ppb increase in summer average ozone for persons with congestive heart failure; of 1.09 (95% CI, 1.06–1.12) with myocardial infarction; of 1.07 (95% CI, 1.04–1.09) with chronic obstructive pulmonary disease; and of 1.07 (95% CI, 1.05–1.10) for diabetics.We also found that the effect varied by region, but that this was mostly explained by mean temperature, which is likely a surrogate of air conditioning use, and hence exposure.
This is the first study that follows persons with specific chronic conditions, and shows that long-term ozone exposure is associated with increased risk of death in these groups.
时间序列研究报告了臭氧与每日死亡人数之间的关联。仅有一项队列研究报告了长期暴露对死亡的影响，而对于臭氧慢性暴露对易感人群生存的影响知之甚少。
我们调查了臭氧是否与美国 105 个城市的四类患有特定疾病人群的生存相关，将臭氧视为随时间变化的暴露因素。
我们使用了 Medicare 数据（1985-2006 年），构建了可能易受臭氧影响的慢性疾病住院患者队列：慢性阻塞性肺疾病、糖尿病、充血性心力衰竭和心肌梗死。将每年暖季的平均臭氧浓度与每个城市的个体随访数据相匹配。我们在每个城市内的每个队列中应用 Cox 比例风险模型，调整了个体风险因素、温度和城市特定的长期趋势。
我们发现臭氧浓度每增加 5ppb，充血性心力衰竭患者的死亡率风险比（95%置信区间为 1.03-1.08）增加 1.06；心肌梗死患者为 1.09（95%置信区间为 1.06-1.12）；慢性阻塞性肺疾病患者为 1.07（95%置信区间为 1.04-1.09）；糖尿病患者为 1.07（95%置信区间为 1.05-1.10）。我们还发现，这种效应因地区而异，但这主要可以用平均温度来解释，平均温度可能是空调使用的替代指标，从而也是暴露的替代指标。
这是第一项针对特定慢性疾病患者的研究，表明长期臭氧暴露与这些人群的死亡风险增加有关。
