Figure 1
Flowchart of the included studies in the systematic review.
Table 1
Basic information of included studies.
| ORDER | AUTHOR (YEAR) | LOCATION | TIME PERIOD | SAMPLE SIZE | GENDER | MEAN OF AGE | TUMOR BY MALIGNANCY | BRAIN TUMOR (n) | M ± SD pm2.5(μg/m3) | M ± SD pm10(μg/m3) | M ± SD NO2(μg/m3) | M ± SD O3(μg/m3) | M ± SD SO2(μg/m3) | M ± SD CO(μg/m3) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | Andersen (2018) | Sweden | 1992–96 | 25 600 | male/female | 45.9 | 63 | 0 | NR | NR | 5.3 (2.5) | NR | NR | NR |
| Norway | 2000–01 | 21 363 | male/female | 48.2 | 39 | 39 | 8.9 (1.3) | 13.5 (3.1) | NR | NR | NR | NR | ||
| Sweden | 1992–2002 | 22 036 | male/female | 56.5 | 37 | NR | 7.1 (1.3) | 14.7 (4.1) | 10.8 (4.6) | NR | NR | NR | ||
| Denmark | 1993–97 | 38 064 | male/female | 56.8 | 200 | 200 | 11.3 (0.8) | 17.2 (1.9) | 16.5 (7.0) | NR | NR | NR | ||
| Netherland | 1993–97 | 36 505 | male/female | 50.3 | 64 | 64 | 16.9 (0.6) | 25.4 (1.5) | 25.2 (6.2) | NR | NR | NR | ||
| Austria | 1985–2005 | 131 907 | male/female | 41.3 | NR | 176 | 13.6 (1.2) | 20.7 (2.4) | 20.0 (5.5) | NR | NR | NR | ||
| Italy | 1993–97 | 11 893 | male/female | 51.6 | 35 | 34 | 43.4 (17.3) | NR | NR | NR | ||||
| Italy (Turin) | 1993–2008 | 8774 | male/female | 50.3 | 28 | 28 | 30.2 (1.6) | 46.6 (4.1) | 53.0 (10.3) | NR | NR | NR | ||
| 2 | Bräuner (2013) | Denmark | 1993–1997 | 51674 | male/female | 56.1 | NR | 121 | NR | NR | 22 | NR | NR | NR |
| 3 | McKean (2009) | United States | 1979–1983 | 383,620 | male/female | 30≤ | NR | 783 | 21.1(4.6) | NR | NR | NR | NR | NR |
| United States | 1999–2000 | 533,960 | male/female | 30≤ | NR | 1,084 | 14.0 (3.0) | NR | NR | NR | NR | NR | ||
| United States | 1982–1998 | 443,765 | male/female | 30≤ | NR | 936 | NR | 28.8(5.9) | NR | NR | NR | NR | ||
| United States | 1982–1999 | 576,315 | male/female | 30≤ | NR | 1,170 | NR | NR | NR | NR | NR | NR | ||
| United States | 1982–2000 | 527,123 | male/female | 30≤ | NR | 1,089 | NR | NR | 21.3(7.1) | NR | NR | NR | ||
| United States | 1982–2001 | 572,829 | male/female | 30≤ | NR | 1,175 | NR | NR | NR | NR | NR | 1.1(0.4) | ||
| United States | 1982–2002 | 560,662 | male/female | 30≤ | NR | 1,135 | NR | NR | NR | 45.5(7.3) | NR | NR | ||
| United States | 1982–1998 | 560,000 | male/female | 30≤ | NR | 1,217 | NR | NR | NR | 59.7(12.8) | NR | NR | ||
| 4 | Raaschou (2011) | Denmark | 1995–2006 | 54304 | male/female | 20.50 | NR | NR | NR | 28/4 | NR | NR | ||
| 5 | Valberg (2010) | United States | 2002–2006 | NR | male/female | NR | NR | 24.60 | r = –0.06 & p-value = 0.26 | r = –0.24 & p-value = 0.0015 | r = 0.15 & p-value = 0.0013 | r = –0.02 & p-value = 0.79 | r = –0.28 & p-value = 0.0002 |
Figure 2
Results of the NOx exposure and incidence of brain tumors.
Figure 3
Results of the Trafnear exposure and incidence of brain tumors.
Figure 4
Results of the O3 exposure and incidence of brain tumors.
Figure 5
Results of the PM2.5 Absorbance exposure and incidence of brain tumors.
Figure 6
Funnel plot for assessment of publication bias.
Table 2
Sub-group analysis based on years of follow-up.
| TYPE OF AIR POLLUTION | LESS THAN TEN YEARS FOLLOW-UP | P-VALUE | MORE THAN TEN YEARS FOLLOW-UP | P-VALUE | OVERALL | P-VALUE |
|---|---|---|---|---|---|---|
| NOx | 1.10 (0.96–1.27) | 0.152 | 1.17 (0.93–1.46) | 0.169 | 1.16 (0.93–1.45) | 0.173 |
| Trafnear | 1.08 (0.99–1.19) | 0.069 | 1.02 (0.87–1.20) | 0.727 | 1.07 (0.99–1.16) | 0.079 |
| PM2.5 Absorbance | 3.08 (1.48–6.39) | 0.003 | 1.11 (0.63–1.96) | 0.699 | 1.63 (1.04–2.55) | 0.031 |
| NO2 | 1.02 (0.86–1.21) | 0.758 | 0.88 (0.81–0.95) | 0.002 | 0.93 (0.77–1.14) | 0.530 |
| PM10 | 1.05 (0.58–1.93) | 0.853 | 0.93 (0.83–1.04) | 0.205 | 0.93 (0.83–1.04) | 0.226 |
| PM2.5 | 0.89 (0.80–1.01) | 0.066 | 0.93 (0.55–1.56) | 0.788 | 0.90 (0.80–1.00) | 0.064 |