Table 1.

Prevalence of DD using random-effects meta-analysis and subgroup meta-analysis.

Variable	No. of Studies	Prevalence (95% CI)	I2, %	p-Value
				Q Test	Egger Test	Begg Test	Subgroup Difference
Global Analysis for DD
DD	56	7.10 [6.27; 7.97]	97.60	<0.001	<0.001	0.05	NA
Gender
boy	41	9.22 [8.07; 10.44]	95.80	<0.001	<0.001	0.35	<0.001
girl	41	4.66 [3.84; 5.54]	95.20	<0.001	<0.001	0.17
Writing system
alphabetic scripts	27	7.26 [5.94; 8.71]	98.10	<0.001	<0.05	0.06	0.74
logographic writing system	31	6.97 [5.86; 8.16]	96.90	<0.001	<0.001	0.27
Orthography depth
shallow orthography	17	7.13 [5.23; 9.30]	98.30	<0.001	<0.05	0.19	0.83
deep orthography	10	7.55 [4.66; 11.04]	97.80	<0.001	<0.05	0.24
Operational definition
1 SD	11	7.10 [4.51; 10.22]	98.40	<0.001	<0.01	0.14	<0.01
1.5 SD	6	5.36 [4.28; 6.55]	87.70	<0.001	NA	NA
2 SD	18	5.32 [4.56; 6.13]	93.70	<0.001	<0.01	0.18
Without reporting SD	23	9.10 [7.18; 11.21]	97.20	<0.001	0.03	0.58
Grade
1	4	7.59 [2.65; 14.72]	96.40	<0.001	NA	NA	0.40
2	7	4.88 [2.94; 7.28]	92.00	<0.001	NA	NA
3	21	6.35 [4.78; 8.13]	95.20	<0.001	0.06	0.15
4	18	5.25 [4.31; 6.27]	85.00	<0.001	0.03	0.12
5	20	7.44 [4.59; 10.90]	98.20	<0.001	0.47	0.01
6	9	4.48 [2.96; 6.29]	93.20	<0.001	NA	NA
Sample size							<0.001
<500	10	7.97 [5.75; 10.51]	84.00	<0.001	0.50	0.53
500–1000	16	8.43 [6.83; 10.18]	90.90	<0.001	0.59	0.72
1000–1500	16	8.25 [6.43; 10.27]	95.80	<0.001	0.15	0.22
1500–3000	6	6.01 [3.84; 8.63]	97.20	<0.001	NA	NA
3000–10,000	6	4.53 [2.81; 6.63]	98.40	<0.001	NA	NA
10,000–	4	3.13 [2.32; 4.06]	98.10	<0.001	NA	NA
Sampling method
cluster sampling	5	5.55 [3.13; 8.60]	98.10	<0.001	NA	NA	0.25
random sampling	37	7.66 [6.60; 8.80]	97.20	<0.001	<0.001	0.80
stratified sampling	16	6.43 [4.84; 8.21]	97.80	<0.001	<0.05	0.05
Sub-deficits
accuracy	8	5.43 [3.91; 7.18]	97.80	<0.001	NA	NA	0.50
accuracy or comprehension	4	7.60 [5.46; 10.06]	88.00	<0.001	NA	NA
accuracy or fluency	5	9.71 [4.29; 16.99]	98.80	<0.001	NA	NA
comprehension	8	7.97 [4.60; 12.15]	98.30	<0.001	NA	NA
fluency	6	6.64 [4.34; 9.37]	92.40	<0.001	NA	NA
Unclassified	27	6.97 [5.77; 8.27]	97.30	<0.001	<0.001	0.44
WHO region
Americas	6	8.11 [4.97; 11.93]	98.80	<0.001	NA	NA	0.97
Eastern Mediterranean	4	6.88 [3.50; 11.27]	95.90	<0.001	NA	NA
Europe	11	6.55 [4.49; 8.97]	98.20	<0.001	<0.05	0.31
South-East Asia and Africa	4	7.11 [3.04; 12.66]	97.50	<0.001	NA	NA
Western Pacific	33	7.16 [6.01; 8.41]	97.30	<0.001	<0.001	0.44
WB region
HIC	18	7.09 [5.54; 8.82]	98.40	<0.001	<0.01	0.43	0.97
MIC	40	7.11 [6.08; 8.20]	97.00	<0.001	<0.001	0.07

Abbreviations: WHO, World Health Organization; WB, World Bank; HIC, high-income countries; MIC, middle-income countries; NA, not applicable.