Table 3

Assessment of bias in single-city studies and in pooled estimates for all-cause, all cardiovascular and all respiratory mortality, in all ages, 24 h NO₂

	All-cause		All cardiovascular		All respiratory
Overall estimate no adjustment for bias*	0.71 (0.43 to 1.00)		0.88 (0.63 to 1.13)		1.09 (0.75 to 1.42)
Single-city bias†
WHO region	EUR A	WPR B	EUR A	WPR B	EUR A	WPR B
p Value Begg	0.87	0.57	0.18	0.65	0.68	0.05
p Value Egger	0.41	0.86	0.16	0.89	0.10	0.23
# Estimates	14	6	10	7	9	5
# Trim and fill	14	7	10	7	11	5
Pooled single-city estimate after trim and fill‡	0.54 (0.31 to 0.77)		0.60 (0.47 to 0.73)		1.16 (0.56 to 1.77)
Multicity bias§
p Value Begg	0.82		0.93		0.66
p Value Egger	0.003		0.12		0.21
# Estimates	11		10		10
# Trim and fill	12		10		15
Overall estimate with adjustment for bias¶	0.64 (0.36 to 0.92)		0.88 (0.63 to 1.13)		0.80 (0.48 to 1.12)

*Random-effects overall estimate (95% CI) per 10 µg/m³ NO₂ (24 h) without adjustment for publication bias.
†Bias in single-city estimates within WHO region: region, Begg's test p value, Egger's test p value, number of estimates prior to adjustment for trim and fill technique, number of estimates after adjustment for trim and fill technique. Assessment of bias in single-city estimates within WHO region was not conducted in regions providing <5 estimates.
‡Overall pooled singe-city estimate calculated after application of the trim and fill technique to the single-city estimates within WHO region.
§Bias between pooled single-city estimates and multicity estimates, Begg's test p value, Egger's test p value, number of estimates prior to adjustment for trim and fill technique, number of estimates after adjustment for trim and fill technique.
¶Overall pooled estimate calculated after application of the trim and fill technique to single-city estimates within WHO region and between pooled single-city estimates and multicity estimates.
EUR, European Region; WPR, Western Pacific Region.