Table 1.
Mean effect sizes for specific health outcomes
| Health outcome | K studies | N subjects | Weighted mean ES | 95% CI | Significance level (p) |
|---|---|---|---|---|---|
| Mortality | 2 | 1,901 | 0.09 | 0.04 to 0.13 | <.001 |
| Survival | 6 | 1,772 | 0.10 | 0.03 to 0.17 | <.001 |
| Cardiovasulcar (cross-sectional and longitudinal studies only) | 8 | 589 | 0.25 | 0.12 to 0.37 | .0002 |
| Cardiovascular (prospective studies only) | 4 | 761 | 0.15 | 0.03 to 0.27 | .01 |
| Physiological markers (cross-sectional and longitudinal studies only) | 8 | 845 | 0.11 | 0.04 to 0.18 | .001 |
| Physiological markers (prospective studies only) | 10 | 961 | 0.17 | 0.07 to 0.27 | .001 |
| Immune function (cross-sectional and longitudinal studies only) | 4 | 312 | 0.12 | −0.01 to 0.24 | .07 |
| Immune function (prospective studies only) | 7 | 251 | 0.21 | 0.05 to 0.36 | .01 |
| Cancer (cross-sectional and longitudinal studies only) | 14 | 2,102 | 0.27 | 0.16 to 0.36 | <.001 |
| Cancer (prospective studies only) | 4 | 756 | 0.07 | −0.001 to 0.14 | .053 |
| Physical symptoms (cross-sectional and longitudinal studies only) | 16 | 2,148 | 0.25 | 0.19 to 0.30 | <.001 |
| Physical symptoms (prospective studies only) | 1 | 242 | 0.16a | – | – |
| Pain (cross-sectional and longitudinal studies only) | 12 | 1,925 | 0.25 | 0.15 to 0.35 | <.001 |
| Pain (prospective studies only) | 3 | 178 | 0.10 | −0.05 to 0.25 | .18 |
| Pregnancy outcomes (cross-sectional and longitudinal studies only) | 2 | 359 | 0.10 | −0.02 to 0.20 | .10 |
| Pregnancy outcomes (prospective studies only) | 1 | 982 | 0.09a | – | – |
a
There is only one study in this category. Thus, a meta-analysis was not conducted. The single effect size is provided for the one study in this category