Table 3.
Results From a Meta-Analysis of Associations Between Ozone Exposure and Mortality and Hospital Admission, by Age, 1988–2013
| No. of Estimate Pairs | No. of Studies | I2 (Uncertainty Parametera), % | 95% CI | P Value (Egger's Regression Test) | Overall Risk Estimate,b % | 95% CI | Overall Estimate Adjusted for Publication Bias,b % | 95% CI | No. of Adjusted Estimates | |
|---|---|---|---|---|---|---|---|---|---|---|
| Total mortality | 35 | 33 | ||||||||
| Younger persons | 66.5 | 52.2, 76.5 | 0.06 | 0.60 | 0.40, 0.80 | 0.55 | 0.34, 0.76 | 4 | ||
| Older persons | 99.9 | 99.9, 100 | 0.48 | 1.27 | 0.76, 1.78 | 1.43 | 0.98, 1.89 | 6 | ||
| Older vs. youngerc | 0.66 | 0.12, 1.12 | 0.16 | 0.07, 0.24 | ||||||
| CVD mortality | 17 | 12 | ||||||||
| Younger | 70.6 | 51.8, 82.0 | 0.48 | 0.53 | 0.20, 0.86 | 0.53 | 0.20, 0.86 | 0 | ||
| Older | 64.4 | 40.2, 78.8 | 0.18 | 0.73 | 0.43, 1.04 | 0.73 | 0.43, 1.04 | 0 | ||
| Older vs. younger | 0.20 | −0.25, 0.65 | 0.20 | −0.25, 0.65 | ||||||
| Respiratory mortality | 16 | 11 | ||||||||
| Younger | 0.0 | 0.0, 23.7 | 0.33 | 0.45 | 0.24, 0.65 | 0.43 | 0.23, 0.64 | 3 | ||
| Older | 8.1 | 0.0, 44.5 | 0.04 | 0.36 | 0.09, 0.63 | 0.32 | 0.03, 0.61 | 5 | ||
| Older vs. younger | −0.09 | −0.42, 0.25 | −0.12 | −0.47, 0.24 | ||||||
| CVD hospitalization | 8 | 8 | ||||||||
| Younger | 72.0 | 42.4, 86.4 | 0.45 | 0.29 | −0.80, 0.22 | 0.29 | −0.80, 0.22 | 0 | ||
| Older | 84.8 | 71.8, 91.8 | 0.16 | 0.57 | −0.05, 1.19 | 0.57 | −0.05, 1.19 | 0 | ||
| Older vs. younger | 0.86 | 0.05, 1.67 | 0.86 | 0.05, 1.67 | ||||||
| Respiratory hospitalization | 12 | 11 | ||||||||
| Younger | 78.3 | 62.5, 87.4 | 0.65 | −0.20 | −0.73, 0.33 | 0.22 | −0.31, 0.76 | 4 | ||
| Older | 77.2 | 60.4, 86.9 | 0.49 | 0.32 | −0.31, 0.96 | 0.32 | −0.31, 0.96 | 0 | ||
| Older vs. younger | 0.52 | −0.31, 1.35 | 0.10 | −0.73, 0.93 | ||||||
| Asthma hospitalization | 8 | 8 | ||||||||
| Younger | 81.9 | 65.5, 90.5 | 0.15 | 2.74 | 0.47, 5.06 | 3.30 | 1.24, 5.40 | 2 | ||
| Older | 61.5 | 16.8, 82.2 | 0.61 | 2.43 | 0.47, 4.42 | 2.43 | 0.47, 4.42 | 0 | ||
| Older vs. younger | −0.31 | −3.20, 2.79 | −0.85 | −3.57, 1.95 |
Abbreviations: CI, confidence interval; CVD, cardiovascular disease.
a Percentage of variance in observed study results explained by heterogeneity.
b Percent increase in risk for a 10-ppb increase in 8-hour ozone concentration.
c Percent increase in ozone risk estimates for older persons compared with younger persons.