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Table 1 Characteristics of the included studies

From: The effect of lead exposure on IQ test scores in children under 12 years: a systematic review and meta-analysis of case-control studies

Author

Year

Country

Number of case group

Number of control group

Mean of IQ score in case group

Standard deviation of case group

Mean of IQ score in control group

Standard deviation of control group

Duration of the lead exposure (year)

Cognitive function measurement

Quality assessment (NOS)

Ibiwari C. Dike

2020

Nigeria

160

40

89.46

13.6

138.24

14.21

1.5

Raven’s standard progressive matrices

Good

Nnenna Linda Nwobi

2019

Nigeria

169

140

86.9

11.6

91.5

14

4

Raven’s standard progressive matrices

Fair

Todd A. Jusko

2008

USA

78

96

91.47

12.6

93.9

14.4

9

Wechsler Preschool and Primary Scale

Good

Pamela J. Surkan

2007

USA

32

357

88.75

12.7

91.92

10.4

4

Wechsler Intelligence Scale for Children -Third Edition (WISC-III)

Good

Katarzyna Kordas

2006

Mexico City

296

293

101.95

15.75

106.4

14.5

3

The testing battery

Fair

Katarzyna Kordas

2004

Mexico City

291

298

103.13

15.06

106.3

14.6

3

Graphic Test of Reasoning (GTR)

Good

Iman Al-Saleh 1

2001

Saudi Arabia

165

368

95.26

14.1

101.39

14.18

6

Beery VMI Saudi-based standard scores

Good

Iman Al-Saleh 2

2001

Saudi Arabia

165

368

93.51

14.61

101.37

15.09

6

TONI Saudi-based scores and rank percentile

Good