Table 2.
Summary risk estimates of cognitive impairment for air pollution according to study characteristics
| Study characteristics |
PM2.5 | RR (95% CI) |
I2 (%) |
Pheterogeneity |
NO2/NOx | RR (95% CI) |
I2 (%) |
Pheterogeneity |
|---|---|---|---|---|---|---|---|---|
| N |
N |
|||||||
| All studies |
11 |
1.08 (1.03, 1.13) |
82.2% |
<0.001 |
7 |
1.02 (0.99, 1.04) |
93.4% |
<0.001 |
| Source of outcome: | ||||||||
| Population-based |
9 |
1.05 (1.01, 1.09) |
57.4% |
0.016 |
5 |
1.048 (1.004, 1.094) |
68.5% |
0.013 |
| Hospital-based |
2 |
1.20 (0.82, 1.75) |
97.1% |
<0.001 |
2 |
0.99 (0.95, 1.02) |
94.7% |
<0.001 |
| Study areas: | ||||||||
| Europe |
5 |
1.34 (0.94, 1.89) |
73.4% |
0.005 |
4 |
1.01 (0.98, 1.05) |
90.1% |
<0.001 |
| North America |
5 |
1.13 (1.01, 1.26) |
86.7% |
<0.001 |
3 |
1.03 (0.98, 1.08) |
66.4% |
0.051 |
| Asia |
1 |
1.01 (0.98, 1.04) |
/ |
/ |
||||
| Follow-up duration: | ||||||||
| ≤10 |
4 |
1.11(0.95, 1.31) |
70.4% |
0.018 |
1 |
1.21 (1.06, 1.35) |
/ |
/ |
| >10 |
7 |
1.10 (1.03, 1.17) |
86.3% |
<0.001 |
4 |
1.01 (0.99, 1.03) |
94.4% |
<0.001 |
| Adjusted comorbidity: | ||||||||
| Yes |
7 |
1.10 (1.03, 1.17) |
85.3% |
<0.001 |
4 |
1.04 (0.99, 1.09) |
72.6% |
0.012 |
| No |
4 |
1.07 (0.90, 1.26) |
64.1% |
0.039 |
3 |
1.00 (0.97, 1.04) |
91.2% |
<0.001 |
| Adjusted smoking: | ||||||||
| Yes |
6 |
1.21 (1.00, 1.46) |
57.0% |
0.040 |
3 |
1.10 (1.02, 1.19) |
53.2% |
0.118 |
| No | 5 | 1.06 (1.01, 1.11) | 90.2% | <0.001 | 4 | 1.00 (0.98, 1.03) | 96.5% | <0.001 |